06.11.2014 1 Gene expression DNA rRNA tRNA mRNA Protein T P +1 18S 5,8S 28S Transcription Processing (autosplicing) 18S 5,8S 28S DNA Pro rRNA 45S rRNAs Steps of the 1 st class genes expression Assembling of RNP 40S + 60S 18S + 33 proteins = 40S 28S + 5,8S + 5S + 49 proteins = 60S
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PowerPoint Presentation · 06.11.2014 1 Gene expression DNA rRNA tRNA mRNA Protein P +1 18S 5,8S 28S T Transcription Processing (autosplicing) 18S 5,8S 28S DNA Pro rRNA 45S rRNAs
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Steps of expression of structural genes(2nd class) in eukaryotes
Transcription of structural genes (2nd class) in eukaryotes
1. Initiation- Assembling of initiation complex (binding of specific and general transcription factors; RNA-polymerase)- Identification of +1 and direction of transcription- local unwinding of DNA- identification of template strand
2. Elongation- RNA-polymerase II reads from DNA information in direction3’-5’- Synthesis of RNA in direction 5’- 3’
3. Termination- Recognition of terminator- RNA-polymerase stops at terminator site- Dissociation of complex RNA-polymerase-RNA-DNA
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-10-20-30-40 +1 +10 +20 +30
TAFs
TFIID
TFIIA
TFIIB
RNA-polymerase II
TFIIF
TFIIE
Initiation of transcription of 2nd class genes
Termination of transcription
T
Capping
Processing of mRNA in eukaryotesE E E EI I I
Pro mRNA
Polyadenylation
7MeGppp
7MeGppp AAAAAA..
mRNA
7MeGppp AAAAAA..
Splicing
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mRNA capping
* Adding of a methylated
GTP (7MeGTP)
* Enzyme gunanine-7-
methyltransferase
* Unusual bond 5’ppp5’
CAP:
! Stabilizes 5’ end of
mRNA
! Represents a site of
recognition of mRNA by
ribosomes
Polyadenylation
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Splicing
Types of mRNA splicing
Electron micro-photography of 1st class genes
transcription in nucleolus
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P O 1 2 3 T5’ 3’
Promoter Operator Terminator
Structural genes
P O 1 2 3 T5’ 3’
Repressor
RNA-polymerase
P O 1 2 3 T5’ 3’
Inductor
Structure of operon (transcription unit in prokariotes)