Genomic organization and polypeptide primary structure of zona pellucida glycoprotein hZP3, the hamster sperm receptor

DEVELOPMENTAL BIOLOGY 142, 414-421 (1990)

Genomic Organization and Polypeptide Primary Structure of Zona Pellucida Glycoprotein hZP3, the Hamster Sperm Receptor

Ross A. KINLOCH, BETINA RUIZ-SEILER, AND PAUL M. WASSARMAN

Department of Cell and Developmental Biology, Roche Institute of Molecular Biology, Roche Research Center, Nutley, New Jersey 07110

Accepted August 29, 1990

During the course of fertilization in mammals, free-swimming sperm bind tightly to receptors located in the egg extracellular coat, or zona pellueida. Recently, the hamster sperm receptor, a 56,000 Mr zona pellucida glycoprotein called hZP3, was identified and partially characterized (C. C. Moller et aL, (1990). Dev. BioL 137, 276-286). Here, we describe genomic cloning of hZP3, certain organizational features of the hZP3 gene, and primary structures of hZP3 mRNA and polypeptide. The findings are compared with reported results of comparable analyses of the mouse sperm receptor, an 83,000 M r zona pellucida glycoprotein called mZP3. Such comparisons reveal a high degree of conservation of genomic organization and polypeptide structure for the two mammalian sperm receptors, despite the considerable difference in their Mrs. These findings are of interest in view of the extremely restricted expression of the ZP3 gene during development and the important role of ZP3 oligosaccharides in gamete adhesion. © 1990 Academic Press, Inc.

INTRODUCTION

Mammalian eggs are surrounded by a thick extracel- lular coat, the zona pellucida (ZP), that plays several impor tant roles during fert i l ization (Gwatkin, 1977; Bedford, 1982; Yanagimachi, 1988). The ZP regulates binding of sperm to eggs, induces bound sperm to acro- some react, and, following sperm-egg fusion, assists in prevention of polyspermy (Yanagimachi, 1988; Wassar- man, 1987a,b, 1988). A mouse ZP glycoprotein, mZP3, serves as both sperm receptor and acrosome reaction inducer during fert i l ization (Wassarman, 1987a,b, 1990). Following zygote formation, inactivation of ZP3 accounts, at least in part, for the role of the ZP in pre- vention of polyspermy (Wassarman, 1987a,b, 1990).

Recently, the hamste r sperm receptor, hZP3, was identified and par t ia l ly characterized (Moller et al., 1990). Interestingly, hZP3 and mZP3 have very different Mrs (56,000 and 83,000, respectively), but are encoded by similarly sized mRNAs (~1.5 kb). These findings are of interest since hamster sperm bind to mouse eggs and mouse sperm bind to hamster eggs (Schmell and Gulyas, 1980; Moller et aL, 1990). In view of this behavior, since mZP3 sperm receptor function is at tr ibutable to a spe- cific size-class of O-linked oligosaccharides (Wassar- man, 1987a,b, 1989, 1990), it is likely tha t mZP3 and hZP3 possess some common oligosaccharide-binding de- terminants.

Various organizational features of the mZP3 gene, as well as primary structures of mZP3 mRNA and polypep- tide, have been reported (Ringuette et al., 1986, 1988; Kinloch et aL, 1988, 1990; Chamberlin and Dean, 1989; Kinloch and Wassarman, 1989a,b). Here, we report that

genomic cloning has enabled us to determine primary structures of hZP3 mRNA and polypeptide, as well as sequences of the hZP3 transcription unit and portions of 5'- and 3'-flanking regions of the hZP3 gene. Conse- quently, certain molecular features of mZP3 and hZP3 genes and polypeptides now can be compared.

MATERIALS AND METHODS

Construction and Screening of Hamster Genomic Library

Hamster (LVG; Mesocricetus auratus; Charles River Breeding Laboratories) spleen DNA was partially di- gested with Sau3A and f ragments were inser ted be- tween the BamHI sites of }, DASH (Stratagene), as de- scribed by Maniatis et al. (1982). The library was ampli- fled on Escherichia coli LE392 and screened by using a a2P-labeled RNA probe specific for mouse ZP3 (Moller et al., 1990). Five positive genomic clones were isolated and one clone, designated hZP3-G37, was characterized.

Subcloning and Sequencing of Genomic DNA Fragments

Four EcoRI fragments of hZP3-G37, 5, 4.6, 4.7, and 0.7 kb in length, were isolated and subeloned into the EcoRI site of pGEM-7Zf ÷ (Promega Biotec) producing plas- mids designated pGEM-hR0, -hRb, -hRa, and -hRc, re- spectively. Similarly, one HindII I fragment , 5 kb in length, was isolated and subcloned into the HindIII site of pGEM-7Zf ÷ (Promega Biotec) producing plasmid pGEM-hH1, and four BamHI /EcoRI f ragments of hZP3-G37, 3.6, 2.57, 2.16, and 1.2 kb in length, were iso- lated and subcloned into the BamHI /EcoRI sites of pGEM-dZ (Promega Biotec) producing plasmids desig-

0012-1606/90 $3.00 Copyright © 1990 by Academic Press, Inc. All rights of reproduction in any form reserved.

414

KINLOCH, RUIZ-SEILER, AND WASSARMAN Hamster Sperm Receptor Gene 415

nated pGEM-hBR1, -hBR2, -hBR3, and -hBR4, respec- tively. Further subcloning of these plasmids was carried out by isolating the desired fragments and cloning them into appropria te ly digested pGEM vectors (Promega Biotec). Sequencing of the pGEM-derived vectors was performed by using dideoxy chain termination (Sanger et al., 1977) and Sequenase kits (United States Biochemical).

Purification of Hamster Ovarian R N A

Ovaries were isolated from 12- to 15-day-old hamsters and homogenized in 2 ml RNAzol B (Cinna/Biotec). Fol- lowing addition of 0.2 ml chloroform, the homogenate was incubated on ice for 5 min and then spun at 12,000g for 15 rain. The aqueous phase was recovered and total RNA isolated by precipitation with an equal volume of isopropanol. Poly(A) ÷ RNA was prepared by mixing to- tal RNA with oligo(dT)-30 latex beads (Nippon Roche) at 37°C for 10 min (Kuribayashi et al., 1988). Following a brief spin, the superna tan t was discarded and beads were resuspended in water and incubated at 65°C for 5 min. Following a brief spin, poly(A) ÷ RNA was recov- ered in the supernatant fraction.

Ribonuclease Protection Assays

RNase protection experiments were carried out as previously described (Kinloch et al., 1988). Briefly, RNA probes were transcribed with SP6 RNA polymerase us- ing HindII I linearized pGEM-hBR2 as template. RNA was mixed with 2 × 106 dpm of RNA probe in 80% form- amide and hybridized overnight at 42°C. Following in- cubation in the presence of RNase A (40 #g/ml) and RNase T1 (2 ~g/ml), protected fragments were analyzed on 6% polyacrylamide/8 M urea sequencing gels.

$1 Nuclease Assays

$1 nuclease assays were carried out as described in Ausabel et al. (1987). Briefly, probes of defined lengths were prepared by primer extension of a 32p-end-labeled oligonucleotide, 5'-CCAGACACTCCACCTCCACGGA- TGA-3' (nt 170-145 of hZP3 exon I), by using pGEM-hR0 as template, digestion of the extended product with Aval , and separation on alkaline, 1.2% low-melting aga- rose gels. A single-stranded probe was recovered from a gel slice and purified by phenol extraction followed by ethanol precipitation. The probe (0.01 pmoles) was hy- bridized to hamster ovarian poly(A) + RNA (1 ttg) or to yeast tRNA (20 ~g) overnight at 30°C in 80% formamide hybridization solution. S1 nuclease (500 U; Bethesda Re- search Laborator ies) was added and protected frag- ments were analyzed on 6% polyacrylamide/8 M urea sequencing gels.

RESULTS

Restriction Map of Hamster ZP3 Genomic Clone

Five genomic clones, designated hZP3-G9, -G15, -G27, -G29, and -G37, were isolated from a hamster Sau3A spleen DNA l ibrary (see Materials and Methods). Southern blot hybridization analyses were carried out by using restriction endonuclease digests of these clones and mouse ZP3 5'- (pGEM-G9/S-A) and 3'- (pZ-C1) probes (Kinloch et aL, 1988; Moller et al., 1990). These analyses revealed that only hZP3-G37 contained the en- tire hZP3 locus. Accordingly, this clone was fully char- acterized by subcloning and sequencing.

Organization of Hamster ZP3 Genomic Clone

Exons comprising the hZP3 gene were located by comparing sequences derived from subclones with the sequence of mZP3 mRNA (Kinloch et al., 1988; Ringuette et al., 1988; Kinloch and Wassarman, 1989a,b). Bound- aries of each exon were defined in the same manner, by comparing splice site donor and acceptor sequences which are extremely well conserved between hamster and mouse.

The hZP3 gene is organized very s imilar ly to the mZP3 gene (Kinloch et al., 1988; Ringuette et al., 1988; Kinloch and Wassarman, 1989a,b; Chamberl in and Dean, 1989). The hZP3 transcription unit (7900 nt) is composed of eight exons (337, 119, 104, 178, 118, 92, 137, and 226 nt, 5' to 3' direction; exons I-VIII) separated by seven introns (Fig. 1). hZP3 exons II, III, V, VI, and VII are identical in size to their mZP3 counterparts, hZP3 exon IV contains a 6 nt deletion, as compared to the corresponding mZP3 exon. hZP3 exons I and VIII have noncoding regions which differ slightly in size from their mZP3 counterparts. With the exception of intron 4, hZP3 introns are also very similar in size (1,950, 1,400, 83, 666, 1,703, 121, and 656 nt, 5' to 3' direction; introns 1-7) to mZP3 introns.

The 5'- and 3'-ends of the hZP3 t ranscr ipt ion unit were mapped by either $1 nuclease or RNase protection analyses (described below). Examination of about 15 kb of hZP3 locus revealed the following (Fig. 1): (i) There is a "TATA box" present 33 nt upstream of the transcrip- tional s tar t site. (ii) The ATG initiation codon is located 29 nt downstream from the 5'-end of the mRNA. (iii) The termination codon TAA forms part of the poly(A) addi- tion signal AATAAA (Proudfoot and Brownlee, 1976), leaving a 17 nt 3'-noncoding region. (iv) There are four tandem repeats of a 54 nt consensus sequence (5'-AGA- GCNCC-TGCCTAGAATCCCCC-AGTGAG-GGGCTG- GGGTGTGGCTCAGTGGT-3 ' ) in the seventh intron. Five copies of this sequence also are located in the 5'- flanking region, at about -2.5 kb, but these copies are

416 DEVELOPMENTAL BIOLOGY VOLUME 142, 1990

[54 nt Repeat]s 'TATA' Box, -33 [54 nt 4 Repeat]. Polyadenylation Signal -2soo ~ 'Chorion.1Box,87 ~ ! A~G, +29 ~3 111 ~

I '°° IIUI[ II JIFII[ I I II III IV V VI VII VIII

337 119 104 178 118 92 137 226

FIG. 1. Organization of the hZP3 gene of LVG hamsters . Eight exons (I-VIII) are denoted by black boxes, with their sizes (nt) indicated below. Seven introns are denoted by open boxes, with thei r sizes (nt) indicated inside. Positions of the "TATA" box, init iat ion codon, polyadenylation signal, tandemly repeated elements, and "chorion box" are indicated. The number ing is given with respect to the s ta r t of t ranscr ipt ion (+1).

oriented in the opposite direction. (v) The sequence 5'- TCACGT-3', located in the 5'-flanking region at -187 nt, is identical to the "chorion box" found in the 5'-flanking region of chorion genes in flies and moths (Levine and Spradling, 1985; Wong et al., 1985; Mitsialis et al., 1987). It is noteworthy that this sequence is present at about the same location in the 5'-flanking region of the hZP3, mZP3 (Kinloch and Wassarman, 1989b), and mZP2 genes (Liang et al., 1990).

Limits of Hamster ZP3 Transcription Unit

$1 nuclease analyses of the 5'-end of hZP3 mRNA re- vealed that ovarian poly(A ÷) RNA protected 169 nt of an antisense probe (Fig. 2). This indicates that hZP3 has an unusually short, 28 nt 5'-noncoding region. RNase pro- tection analyses were carried out by using ovarian poly(A ÷) RNA and antisense probes complementary to either the whole of exon VIII (Fig. 2) or a f ragment of exon VIII terminating at a BglI site (data not shown). In the former case a 226 nt fragment was protected and in the latter a 130 nt fragment was protected. This indi- cates that hZP3 has an unusually short, 17 nt 3'-noncod- ing region. It should be noted that two other protected fragments observed in Fig. 2 correspond to exons VI and VII, and their lengths (92 and 137 nt, respectively) are exactly those predicted from the sequence data de- scribed above. This correspondence supports the effi- cacy of RNase protection analyses to define the length of exon VIII.

Sequence of Hamster ZP3 Messenger R N A and Polypeptide

Sequences of the eight hZP3 exons can be combined to produce an mRNA of 1311 nt (Fig. 3). Translation of this sequence reveals a single open reading frame, 1266 nt,

encoding 422 amino acids (45,805 Mr; pI 6.6) (Fig. 3). The N-terminal 22 amino acids are predicted to form a sig- nal sequence (yon Heijne, 1986) that would be missing from the mature hZP3 polypeptide (400 amino acids; 43,504 Mr; pI 6.5). Aside from its mouse counterpart, mZP3, hZP3 is not significantly similar to any entries in either GenBank or Protein Identification Resources data bases.

DISCUSSION

Comparative Organizational Features of hZP3 and mZP3 Genes

(i) hZP3 and mZP3 transcription units, 7900 and 8508 nt, respectively, both consist of eight exons and seven introns, hZP3 mRNA contains 1266 nt of coding se- quence, 6 nt less than mZP3 mRNA. The 5'- and 3'-non- coding regions of both hZP3 and mZP3 mRNAs, and of mZP2 mRNA (Liang et al., 1990), are very short as com- pared to most eukaryotic mRNAs (Kozak, 1984).

(ii) Ten nucleotides around the ATG initiation codon of hZP3 and mZP3 genes match those of a consensus sequence (gccGCCA/GCCATGG) reported to be in- volved in translation initiation in vertebrates (Kozak, 1987). The termination codon TAA forms part of the poly(A) addition signal, AATAAA (Proudfoot and Brownlee, 1976), for both hZP3 and mZP3 genes.

(iii) The sequence 5'-TGTGTCTG-3', located 34 and 26 nt downstream from the poly(A) addition site of hZP3 and mZP3 genes, respectively, is similar to the consen- sus element 5'-YGTGTTYY-3' (Y is a pyrimidine) thought to be involved in determining the 3'-end of many polyadenylated mammalian mRNAs (McLauch- lan et al., 1985).

(iv) Several copies of a 54 nt consensus sequence are found as tandem arrays in the 5'-flanking regions and

KINLOCH, RUIZ-SEILER, AND WASSARMAN Hamster Sperm Receptor Gene 417

G A T C 0 Y Y 0 O

2 2 6 - ~

~-'169

137"~

92"~

A T C A.

FIG. 2. Mapping 5'- and 3'-ends of the hZP3 transcr ipt ion unit. (A) $1 nuclease analysis of 5'-end. A 82P-end-labeled, single-stranded DNA probe (corresponding to par t of exon I and a portion of 5'-flanking sequence) synthesized by pr imer extension of an oligonucleotide (25 mer) and cleaved with AvaI, was t reated with $1 nuclease in the pres- ence of either yeast (Y; 10 ttg) or ovarian (O; 1 ttg) RNA. Protected f ragments were separated by electrophoresis on 6% polyacrylamide-8 M urea gels. Lanes G, A, T, and C contain dideoxy sequencing reac- tions primed with the same oligonucleotide used to make the probe. (B) RNase protection analysis of 3'-end. A uniformally 82P-labeled an- tisense RNA probe, t ranscr ibed from HindIII digested pGEM-hBR2, was annealed with ei ther yeast (Y; 10 tLg) or ovarian (0; 10 tLg) RNA and treated with RNase A and RNase T1. Protected f ragments were separated by electrophoresis on 6% polyacrylamide-8 M urea gels. Lanes G, A, T, and C contain dideoxy sequencing reactions of pGEM- hBR2 used as size markers. Sizes of f ragments (nt) are indicated.

seventh introns of both hZP3 and mZP3 genes. Copies of this repeated sequence are more than 75% identical to one another. In CD-1 mice, six copies are located be- tween nt -508 and -826 upstream of the transcriptional

s tar t site, and four copies are present in the seventh intron (Kinloch and Wassarman, 1989a, b; Kinloch et al., 1988). [In B10.A(F1) mice, six copies are present in the 5'-flanking region and five copies in the seventh intron (Chamberlin and Dean, 1989).] In hamsters, five copies of this consensus sequence are found in tandem, but in the opposite orientation as compared to that in mouse, about 2500 nt upstream of the transcription s tar t site. Four copies, present in the same orientation and located about the same distance from exon VII as in mice, are found in the seventh intron. Conservation of this re- peated sequence suggests that it may be involved in reg- ulating oocyte-specific expression of the ZP3 gene. Tan- dem repeats function in the regulation of expression in several systems, and enhancer function often requires multiple sequence motifs, although not necessarily as tandem repeats (reviewed in Kinloch and Wassarman, 1989b).

(v) Expression of the mZP3 gene is restricted exclu- sively to growing oocytes (Philpott et aL, 1988; Roller et al., 1989; Kinloch and Wassarman, 1989b) and cis-acting elements present in the gene's 5'-flanking region regu- late oocyte-specific expression (Lira et al., 1990). Pre- sumably, identical elements also regulate expression of the hZP3 gene. In this context, sequences just upstream of the initiation codons of mZP3 and hZP3 genes (210 nt) are extremely similar (~85%); this includes a stretch of 94 nt that is 93% identical.

Comparative Structural Features o f hZP3 and m Z P 3 Polypeptides

(i) The predicted primary structure of hZP3 polypep- tide consists of 422 amino acids, with the N-terminal 22 amino acids, as in the case of mZP3, forming a signal sequence. The latter consists of a short polar domain followed by a hydrophobic domain of 11 amino acids. The four amino acids around the cleavage site conform to the " -3 , - 1 rule" for predict ing signal sequence- cleavage sites (yon Heijne, 1986) and, except for the - 2 position, are identical to the corresponding mZP3 resi- dues.

(ii) Processing of the signal sequence leaves a mature hZP3 polypeptide consisting of 400 amino acids. Overall, hZP3 polypeptide is 81% identical to mZP3 polypeptide which consists of 402 amino acids (Kinloch et al., 1988; Ringuette et al., 1988). Excellent alignment of the two polypeptides is achieved by deleting leucine-223 and proline-224 of mZP3. Only one small region of hZP3 poly- peptide (residues 318-356) is significantly different (~50%) from mZP3 polypeptide.

(iii) Like its mouse counterpart, hZP3 polypeptide is rich in serine plus threonine (hZP3, ~19%; mZP3, ~17%) and proline (hZP3, ~7%; mZP3, ~7%) , as com-

418 DEVELOPMENTAL BIOLOGY VOLUME 142, 1990

5'-ATGCAGCGGGCCTTATTCAGGCAGTACC

ATG GGG CTG AGC TAC CAG CTC CTC CTG TGT CTC CTG CTG TGT GGA GGC GCC AAG CAG TGC MET GLY LEU SER TYR GLN LEU LEU LEU CYS LEU LEU LEU CYS GLY GLY ALA LYS GLN CYS 1 2O TGT TCC CAG CCT CTG TGG CTC TTG CCA GGC GGA ACT CCG ACC CCA GGA AAG CTC ACG TCA CYS SER GLN PRO LEU TRP LEU LEU PRO GLY GLY THR PRO THR PRO GLY LYS LEU THR SER 21 40 TCC GTG GAG GTG GAG TGT CTG GAA GCT GAG CTC GTG GTG ATC GTC AGT AGA GAC CTT TTT SER VAL GLU VAL GLU CYS LEU GLU ALA GLU LEU VAL VAL THR VAL SER ARG ASP LEU PHE 41 60 GGC ACC GGG AAG CTC ATA CAG CCC GAG GAC CTC ACC CTT GGC TCA GAA AAC TGT CGG CCC GLY THR GLY LYS LEU ILE GLN PRO GLU ASP LEU THR LEU GLY SER GLU ASN CYS ARG PRO 61 80 CTG GTT TCC GTG GCT ACG GAT GTG GTC AGG TTC AAG GCC CAG TTG CAT GAA TGC AGC AAC LEU VAL SER VAL ALA THR ASP VAL VAL ARG PHE LYS ALA GLN LEU HIS GLU CYS SER ASN 81 i00 AGG GTG CAG GTG ACG GAA GAT GCC CTG GTG TAC AGC ACC GTG CTG CTG CAC CAA CCC CGC ARG VAL GLN VAL THR GLU ASP ALA LEU VAL TYR SER THR VAL LEU LEU HIS GLN PRO ARG i01 120 CCT GTG CCC GGC CTG TCC ATC CTG AGG ACT AAC CGT GCG GAC GTG CCT ATT CAG TGC CGC PRO VAL PRO GLY LEU SER ILE LEU ARG THR ASN ARG ALA ASP VAL PRO ILE GLU CYS ARG 121 140 TAC CCC AGG CAG GGC AAT GTG AGC AGC CAC GCT ATC CGG CCC ACC TGG GTT CCC TCT AGG TYR PRO ARG GLN GLY ASN VAL SER SER HIS ALA ILE ARG PRO THR TRP VAL PRO PHE SER

141 160 ACC ACT GTG TCC TCA GAG GAG AAG CTG GTT TTC TCT CTC CGC CTG ATG GAG GAG AAC TGG THR THR VAL SER SER GLU GLU LYS LEU VAL PHE SER LEU ARG LEU MET GLU GLU ASN TRP 161 180 AAC ACT GAG AAA TTG TCA CCC ACC TCC CAC CTG GGA GAG GTA GCC TAC CTC CAG GCA GAG ASN THR GLU LYS LEU SER PRO THR SER HIS LEU GLY GLU VAL ALA TYR LEU GLN ALA GLU 181 200 GTC CAG ACT GGA AGC CAT CTG CCA CTG CTG CTG TTT GTG GAG CGC TGT GTG GCC ACA CCT VAL GLN THR GLY SER HIS LEU PRO LEU LEU LEU PHE VAL ASP ARG CYS VAL ALA THR PRO 201 220 TCG CCG GAC CAG ACC GCC TCT CCC TAT CAT GTC ATT GTG GAC TTC CAT GGT TGC CTT GTG SER PRO ASP GLN THR ALA SER PRO TYR HIS VAL ILE VAL ASP PHE HIS GLY CYS LEU VAL 221 240 GAT GGT CTA TCT GAG AGC TTT TCT GCA TTT CAA GTG CCT AGA CCC CGG CCG GAG ACT CTT ASP GLY LEU SER GLU SER PHE SER ALA PHE GLU VAL PRO ARG PRO ARG PRO GLU THR LEU 241 260 CAG TTC ACG GTG GAT GTA TTC CAT TTT GCC AAT AGC TCC AGA AAT ACG ATC TAT ATC ACC GLN PHE THR VAL ASP VAL PHE HIS PHE ALA ASN SER SER ARG ASN THR ILE TYR ILE THR

261 280 TGT CAT CTC AAA GTC ACC CCA GCC AAC CAG ACC CCA GAT GAG CTC AAC AAA GCC TGC TCC CYS HIS LEU LYS VAL THR PRO ALA ASN GLN THR PRO ASP GLU LEU ASN LYS ALA CYS SER

281 300 TTC AAC AGG TCT TCC AAG AGT TGG TCG CCA GTA GAG GGC GAT GCT GAG GTC TGC GGC TGC PHE ~SN LYS SER SER LYS SER TRP SER PRO VAL GLU GLY ASP ALA GLU VAL CYS GLY CYS

301 320 TGC AGC AGT GGC GAC TGT GGT AGC TCA AGC CGT TCA CGG TAC CAG GCC CAT GGA GTG AGC CYS SER SER GLY ASP CYS GLY SER SER SER ARG SER ARG TYR GLN ALA HIS GLY VAL SER 321 340 CAG TGG CCC AAG TCG GCA TCT AGA CGC CGC AGG CAC GTG AGA GAC GAA GCT GAT GTC ACG GLN TRP PRO LYS SER ALA SER ARG ARG ARG ARG HIS VAL ARG ASP GLU ALA ASP VAL THR 341 360 GTA GGA CCC CTG ATC TTC CTG GGA AAG GCA AGC GAC CAG GCT GTG GAG GGC TGG GCC TCT VAL GLY PRO LEU ILE PHE LEU GLY LYS ALA SER ASP GLN ALA VAL GLU GLY TRP ALA SER 361 380 TCT GCT CA/{ ACC TCT TTG GCT CTT GGT TTA GGC CTA GCC GCA GTG GCA TTC CTG ACC CTG SER ALA GLN THR SER LEU ALA LEU GLY LEU GLY LEU ALA ALA VAL ALA PHE LEU THR LEU 381 400 GCT GCT ATT GTC CTC GGT GTC ACC AGG AGT TGT CAC ACC CCT TCC CAT GTT GTA TCC CTT ALA ALA ILE VAL LEU GLY VAL THR ARG SER CYS HIS THE PRO SER HIS VAL VAL SER LEU 401 420 TCA CAATAAAAAGTCCAGTTCTG-3'

SER GLN 421

Fro. 3. Primary structure of hZP3 mRNA (top) and polypeptide (bottom). The predicted signal sequence (residues 1-22) is italicized and locations of potential N-linked glycosylation sites (Asn-X-Ser/Thr) are underlined.

pared to that in the average vertebrate protein (Doolit- tle, 1986). Interestingly, all 13 cysteine residues in mZP3 are conserved in hZP3, suggesting that they may be in- volved in intramolecular disulfide formation and im-

pose important structural constraints. Also, like mZP3 (Kinloch et al., 1988; Kinloch and Wassarman, 1989b), the middle third of hZP3 polypeptide is a proline-poor domain (residues 159-207, 1 proline) sandwiched be-

KINLOCH, RUIz-SEILER, AND WASSARMAN Hamster Sperm Receptor Gene 419

M MASSYFLFL~LLL~GGPEL~NSQTLWLLPG 30

H .GL..Q.L ........ AKQ.[..P ......

M GTPTPVGSSSPVKVE~LEAELVVTVSRDLF 60

H ..... GKLT.S.E .................

M GTGKLVQP GD LTLGSEGCQPRVSVDTDVVR 90

H ..... I..E ....... N.R.L...A .....

M FNAQLHE~SSRVQMTKDALVYSTFLLHDPR 120

H .K ....... N...V.E ....... V...Q..

M PVSGLSILRTNRVEVPIE[RYPRQGNVSSH 150

H ..P ......... AD ................

M PIQPTWVPFRATVSSEEKLAFSLRLMEENW 180

H A.R ...... ST ........ V ..........

M NTEKSAPTFHLGEVAHLQAEVQTGSHLPLQ 210

H .... LS..S ...... Y ............. L

M LFVDH~VATPSPLPDPNSSPYHFIVDFHG~ 240

H .... R ....... --.QTA .... V .......

M LVDGLSESFSAFQVPRPRPETLQFTVDVFH 270

H ..............................

M FANSSRNTLYITCHLKVAPANQIPDKLNKA 300

H ........ I ........ T .... T..E ....

M ~SFNKTSQSWLPVEGDADICDCCSHGNCS~ 330

H ..... S.K..S ...... EV.G...S.D.GS

M SSSSQFQIHGPRQWSKLVSRNRRHVTDEAD 360

H ..R.RY.A..VS..P.SA..R .... R ....

M VTVGPLIFLGKANDQTVEGWTASAQTSVAL 390

H ............ S..A .... AS ..... L..

M GLGLATVAFLTLAAIVLAVTRK~HSSSYLV 420

H ..... A ........... G...S..TP.HV.

M SLPQ 424

H ..S.

FIG. 4. Comparison of pr imary s t ructures of mZP3 and hZP3 poly- peptides. The single-letter amino acid code is used. Mouse (designated M) and hamster (designated H) polypeptides are aligned so as to pro- vide maximum similari ty between the polypeptides. The entire mZP3 amino acid sequence is shown. For hZP3, only those positions where the amino acid sequence differs from mZP3 are shown in the single- letter code. A two-amino acid deletion in hZP3 is indicated by dashes at positions 223 and 224 of mZP3. The predicted signal sequences are italicized (residues 1-22), and locations of cysteine residues (C) and potential N-linked glycosylation sites (N) are underlined.

tween two proline-rich domains (residues 119-158, 7 prolines; residues 208-257, 7 prolines). Conservation of these domains in hZP3 and mZP3 could have functional implications.

(iv) hZP3 polypeptide has four potential N-linked gly- cosylation sites (consensus sequence Asn-Xaa-Ser/Thr) (Struck and Lennarz, 1980; Kornfeld and Kornfeld, 1985). Three of the four sites are conserved between hZP3 and mZP3; the latter has six potential N-linked glycosylation sites, of which a maximum of four are used (Salzmann et al., 1983; Kinloch et al., 1988; Rin- guet te et al., 1988). It is unclear how many hZP3 N- linked glycosylation sites are used, but three are pre-

dicted to be located at reverse turns or coils, where the majori ty of N-linked oligosaccharides are found (Struck and Lennarz, 1980).

(v) Secondary s t ructure prediction methods (Chou and Fasman, 1978; Garnier et al., 1978) suggest tha t hZP3 polypeptide, like mZP3 polypeptide (Kinloch et al., 1988), contains little a-helix-forming potential. Rather, it consists of short segments of extended chain in- terrupted by reverse turns or coils. Hydrophobicity pro- files (Kyte and Doolittle, 1982) for hZP3 and mZP3 are virtually identical.

(vi) A recent comparison of mZP3 and mZP2 polypep- tides has revealed that, although there is no overall se- quence similarity, there are two 5-amino acid stretches tha t are common to both polypeptides (Liang et al., 1990). One (Val-Ser-Leu-Pro-Gln) is located at the N- terminus of mZP2 and at the C-terminus of mZP3, and the other (Thr-Leu-Gly-Ser-Glu) is located about 70 resi- dues from the N-terminus of mZP2 and mZP3. While the lat ter sequence is conserved in hZP3 (residues 72-76), the former is changed to Val-Ser-Leu-Ser-Gln in hZP3 (residues 418-422). An additional 4-amino acid stretch common to mZP2 (residues 228-231) and mZP3 (resi- dues 416-419), Ser-Ser-Tyr-Leu, is changed to Pro-Ser- His-Val in hZP3 (residues 414-417).

FINAL COMMENTS

Since hZP3 and mZP3 polypeptides have nearly iden- tical Mrs, the rather large difference in Mrs of the glyco- proteins is apparently due to a difference in the extent of glycosylation. As yet, hZP3 oligosaccharides have not been thoroughly characterized. However, it has been found that certain mZP3 O-linked oligosaccharides are responsible for sperm receptor function (Wassarman, 1987a,b, 1989, 1990) and that mouse and hamster ga- metes interact with one another in v i tro (Schmell and Gulyas, 1980; Cherr et al., 1986; Uto et al., 1988; Moller et al., 1990). These findings suggest that hZP3, although under-glycosylated as compared with mZP3, possesses O-linked oligosaccharides in common with mZP3. Un- like the N-linked glycosylation pathway, for which sev- eral essential parameters have been defined (Struck and Lennarz, 1980; Kornfeld and Kornfeld, 1985), the O- linked glycosylation pathway remains relatively unde- fined. Experimental manipulations of mZP3- and hZP3- cloned genes may provide some insight into the O-linked glycosylation pathway in mammalian cells. In addition, since hZP3 contains considerably less ca rbohydra te than mZP3, it may prove to be bet ter suited to struc- ture-function studies.

It is estimated that mice and hamsters diverged about 37 million years ago (De Jong, 1985). It is also estimated that the frequency of amino acid change per unit time in

420 DEVELOPMENTAL BIOLOGY VOLUME 142, 1990

evolution is 0.1-1.0 amino acid/102 residues per 106 years (i.e., 0.1-1% sequence divergence/106 years) (Darnell et al., 1986). Eighty-five amino acids of the hZP3 polypep- tide differ from those of the mZP3 polypeptide (424 amino acids) (Fig. 4). Thus, the pr imary structures of these sperm receptors exhibit a normal rate of sequence divergence ([85/4.24]/37 = 0.54 amino acids/102 residues per 106 years; 0.54% sequence divergence/106 years). De- spite these changes, it is likely that the three-dimen- sional structures of hZP3 and mZP3 are very similar to one another (discussed above).

We are grateful to all members of our laboratory for advice and constructive criticism throughout the course of this research. We also thank Dr. Vic Vacquier and the anonymous referees for improving the final version of this report. One of us (B.R.-S.) was supported in part by a postdoctoral fellowship from Schering AG,

REFERENCES

AUSUBEL, F. M., BRENT, R., KINGSTON, R. E., MOORE, D. D., SEIDMAN, J. G., SMITH, J. A., and STRUHL, K. (1987). "Short Protocols in Molec- ular Biology", pp. 150-153. Wiley-lnterscience, New York.

BEDFORD, J. M. (1982). Fertilization. In "Reproduction in Mammals" (C. R. Austin, and R. V. Short, Eds.), Vol. I, pp. 128-163. Cambridge Univ. Press, Cambridge.

CHAMBERLIN, M. E., and DEAN, J. (1989). Genomic organization of a sex-specific gene: The primary sperm receptor of the mouse zona pellucida. Dev. BioL 131,207-214.

CHERR, G. N., LAMBERT, H., MEIZEL, S., and KATZ, D. F. (1986). Invitro studies of the golden hamster sperm acrosome reaction: Completion on the zona pellucida and induction by homologous soluble zonae pellucidae. Dev. BioL 114, 119-131.

CHOU, P. Y., and FASMAN, G. D. (1978). Prediction of the secondary structure of proteins from their amino acid sequence. Adv. Enzy- mol. 47, 47-148.

DARNELL, J., LODISH, H., and BALTIMORE, D. (1986). "Molecular Cell BiologY." Scientific American Books, New York.

DE JONG, W. W. (1985). Superordinal affinities of rodentia studied by sequence analysis of eye lens protein. In "Evolutionary Relation- ships Among Rodents--A Multidisciplinary Analysis" (W. P. Luck- ett, and J.-L. Hartenberger, Eds.), pp. 211-226. Plenum, New York.

DOOLITTLE, R. F. (1986). "Of Urfs and Orfs." Univ. Science Books, Mill Valley, CA.

GARNIER, J., OSGUTHORPE, D., and ROBSON, B. (1978). Analysis of the accuracy and implications of simple methods for predicting the sec- ondary structure of globular proteins. J. Mol. BioL 120, 97-120.

GULYAS, B. J., and SCHMELL, E. D. (1981). Sperm-egg recognition and binding in mammals. In "Bioregulators of Reproduction" (G. Ja- giello, and H. J. Vogel, Eds.), pp. 499-519. Academic Press, New York.

GWATKII~, R. B. L. (1977). "Fer t i l izat ion Mechanisms in Man and Mammals." Plenum, New York.

KINLOCH, R. A., ROLLER, R. J., FIMIANI, C. M., WASSARMAN, D. A., and WASSARMAN, P. M. (1988). Primary structure of the mouse sperm receptor's polypeptide chain determined by genomic cloning. Proc. Natl. Acad. Sci. USA 85, 6409-6413.

KINLOCH, R. A., ROLLER, R. J., and WASSARMAN, P. M. (1990). Organi- zation and expression of the mouse sperm receptor gene. In "Devel- opmental Biology," (E. Davidson, J. Ruderman, and J. Posakony,

Eds.), UCLA Symp. Mol. Cell. Biol. No. 125, pp. 9-20. A. L. Liss, New York.

KINLOCH, R. A., and WASSARMAN, P. M. (1989a). Nucleotide sequence of the gene encoding EDna pellucida glycoprotein ZP3--the mouse sperm receptor. Nucleic Acids Res. 17, 2861-2863.

KINLOCH, R. A., and WASSARMAN, P. M. (1989b). Profile of a mamma- lian sperm receptor gene. New Biol. l, 232-238.

KORNFELD, R., and KORNFELD, S. (1985). Assembly of asparagine- linked oligosaccharides. Annu. Rev. Biochem. 54, 631-664.

KOZAK, M. (1984). Compilation and analysis of sequences upstream from the translational s tar t site in eukaryotic mRNAs. Nucleic Acids Res. 12, 857-872.

KOZAK, M. (1987). An analysis of 5'-noncoding sequences from 699 vertebrate messenger RNAs. Nucleic Acids Res. 15, 8125-8131.

KURIBAYASHI, K., HIKATA, M., IRAOKA, 0., MIYAMOTO, C., and FURUI- CHI, Y. (1988). A rapid and efficient purification of poly(A)-mRNA by oligo(dT)30-1atex. Nucleic Acids Res. Symp. 19, 61-64.

KYTE, J., and DOOLITTLE, R. F. (1982). A simple method for displaying the hyropathic character of a protein. J. Mol. Biol. 157, 105-132.

LEVINE, J., and SPRADLING, A. C. (1985). DNA sequence of a 3.8 kb region controlling Drosophila chorion gene amplification. Chromo- soma 92, 136-142.

LIANG, L.-F., CHAMOW, S. M., and DEAN, J. (1990). Oocyte-specific ex- pression of mouse Zp-2." Developmental regulation of the EDna pellu- cida genes. MoL Ceil BioL 10, 1507-1515.

LIRA, S. A., KINLOCH, R. A., MORTILLO, S., and WASSARMAN, P. M. (1990). An upstream region of the mouse ZP3 gene directs expres- sion of firefly luciferase specifically to growing oocytes in trans- genic mice. Proc. Nail Acad. Sei. USA 87, 7215-7219.

MANIATIS, T., FRITSCH, F. F., and SAMBROOK, J. (1982). "Molecular Cloning: A Laboratory Manual." Cold Spring Harbor Laboratory, Cold Spring Harbor, NY.

MCLAUCHLAN, J., GAFFNEY, D., WHI2"rEN, G. L., and CLEMENTS, J. B. (1985). The consensus sequence YGTGTTYY located downstream from the AATAAA signal is required for efficient formation of mRNA 3' termini. Nucleic Acids Res. 13, 1347-1368.

MITSIALIS, S. A., SPOEREL, N. A., LEVITEN, N. A., and KAFATOS, F. C. (1987). A short 5'-flanking DNA region is sufficient for developmen- tally correct expression of moth chorion genes in Drosophila. Proc. Natl. Aca& Sci. USA 84, 7987-7991.

MOLLER, C. C., BLEIL, J. D., KINLOCH, R. A., and WASSARMAN, P. M. (1990). Structural and functional relationships between mouse and hamster EDna pellucida glycoproteins. Dev. Biol. 137, 276-286.

MOUNT, S. M. (1982). A catalogue of splice junction sequences. Nucleic Acids Res. 10, 459-472.

PHILPOTT, C. C., RINGUETTE, M. R., and DEAN, J. (1988). Oocyte-speci- fic expression and developmental regulation of ZP-3, the sperm re- ceptor of the mouse EDna pellucida. Dev. Biol. 121, 568-575.

PROUDFOOT, N. J., and BROWNLEE, G. G. (1976). 3'-Non-coding region sequences in eukaryotic messenger RNA. Nature (London) 263, 211- 214.

RINGUETTE, M. J., CHAMBERLIN, M. E., BAUR, A. W., SOBIESKI, D. A., and DEAN, J. (1988). Molecular analysis of cDNA coding for ZP3, a sperm binding protein of the mouse EDna pellucida. Dev. Biol. 127, 287-295.

RINGUETTE, M. J., SOBIESKI, D. A., CHAMOW, S. M., and DEAN, J. (1986). Oocyte-specific gene expression: Molecular characterization of a cDNA coding for ZP-3, the sperm receptor of the mouse zona pellucida. Proc. Natl. Acad. Sci. USA 83, 4341-4345.

ROLLER, R. J., KINLOCH, R. A., HIRAOKA, B. Y., LI, S.S.-L., and WAS- SARMAN, P. M. (1989). Gene expression during mammalian oogene- sis and early embryogenesis: Quantification of three messenger

KINLOCH, RUIZ-SEILER, AND WASSARMAN Hamster Sperm Receptor Gene 421

RNAs abundant in fully grown mouse oocytes. Development 106, 251-261.

SANGER, F., NICKLEN, S., and COULSON, A. R. (1977). DNA sequencing with chain-terminating inhibitors. Proc. Natl. Acad. Sci. USA 74, 5463-5467.

SALZMANN, G. S., GREVE, J. M., ROLLER, R. J., and WASSARMAN, P. M. (1983). Biosynthesis of the sperm receptor during oogenesis in the meuse. Eur. MoL BioL Org. J. 2, 1451-1456.

SCHMELL, E., and GULYAS, B. J. (1980). Mammalian sperm-egg recogni- tion and binding in vitro. I. Specificity of sperm interaction with live and fixed eggs in homologous and heterologous inseminations of hamster, mouse, and guinea pig oocytes. Biol. Reprod. 23,1075-1085.

STRUCK, D. K., and LENNARZ, W. J. (1980). The function of saccharide- lipids in synthesis of glycoproteins. In "The Biochemistry of Glyco- proteins and Proteoglycans" (W. J. Lennarz, Ed.), pp. 35-84. Ple- num, New York.

UTO, N., YOSHIMATSU, N., LOPATA, A., and YANAGIMACHI, R. (1988). Zona-induced acrosome reaction of hamster spermatozoa. J. Exp. Zool. 248, 113-120.

VON HEIJNE, G. (1986). A new method for predicting signal sequence cleavage sites. Nucl. Acids Res. 14, 4683-4690.

WASSARMAN, P. M. (1987a). The biology and chemistry of fertilization. Science 235, 553-560.

WASSARMAN, P. M. (1987b). Early events in mammalian fertilization. Annu. Rev. Cell Biol. 3, 109-142.

WASSARMAN, P. M. (1988). Zona pellucida glycoproteins. Annu. Rev. Biochem. 57, 415-442.

WASSARMAN, P. M. (1989). Carbohydrate-mediated sperm-egg inter- actions during mammalian fertilization. Ciba Foundation Syrup. 145, 135-155.

WASSARMAN, P. M. (1990). Profile of a mammalian sperm receptor. Development 108, 1-17.

WONG, Y. C., PUSTELL, J., SPOEREL, N., and KAFATOS, F. C. (1985). Coding and potential regulatory sequences of a cluster of chorion genes in Drosophila melanogaster. Chromosoma 92, 124-135.

YANAGIMACHI, R. (1988). Mammalian fertilization. In "The Physiol- ogy of Reproduction" (E. Knobil, and J. Neill, Eds.), Vol. 1, pp. 135- 185. Raven Press, New York.