RNA processing in eukaryotes DNA promoter exons introns primary transcript (nucleus) 5’ cap AAAAAAAAA 3’ poly - A tail AAAAAAAAA splicing splicing transcription transcription unbroken coding sequence transport to cytoplasm for translation transport to cytoplasm for translation final mRNA
45
Embed
RNA processing in eukaryotes DNA promoter exons introns primary transcript (nucleus) 5’ cap AAAAAAAAA 3’ poly-A tail AAAAAAAAA splicing transcription unbroken.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
RNA processing in eukaryotes
DNA
promoter
exons introns primary transcript(nucleus)
5’ capAAAAAAAAA3’ poly-A tail
AAAAAAAAA
splicingsplicing
transcriptiontranscription
unbroken coding sequence
transport to cytoplasm for translationtransport to cytoplasm for translation
final mRNA
methylated guanine “backward” 5′ to 5′ linkage Not encoded in DNA Capping enzyme Recognition by ribosome
5′ cap
5′ AGACCUGACCAUACC
RNA processing in eukaryotes
DNA
promoter
exons introns primary transcript(nucleus)
5’ capAAAAAAAAA3’ poly-A tail
AAAAAAAAA
splicingsplicing
transcriptiontranscription
unbroken coding sequence
transport to cytoplasm for translationtransport to cytoplasm for translation
final mRNA
3′ poly(A) tail Poly(A) polymerase Add ~200 A’s Not in template Important for:
Export of mRNA Initiation of Translation Stability of mRNA
…UGGCAGACCUGACCA 3′
…UGGCAGACCUGACCAAAAAAAAAAAAAAAAAAAA
RNA processing in eukaryotes
DNA
promoter
exons introns primary transcript(nucleus)
5’ capAAAAAAAAA3’ poly-A tail
AAAAAAAAA
splicingsplicing
transcriptiontranscription
unbroken coding sequence
transport to cytoplasm for translationtransport to cytoplasm for translation
final mRNA
Splicing Most genes interrupted by introns Introns removed after transcription Exons spliced together
5’ capAAAAAAAAA3’ poly-A tail
AAAAAAAAA
splicingsplicing
unbroken coding sequencefinal mRNA
Splicing snRNPs recognize exon-intron
boundaries RNA + protein Cut and rejoin mRNA
Splicing
RPE65 mRNA in nucleus: 21,000 nt (14 exons)
AAAAAAAAA
AAAAAAAAA
splicingsplicing
mature RPE65 mRNA in nucleus: 1,700 nt (8%)
Splicing Alternative splicing: >1 protein from one gene 27,000 human genes, but >100,000 proteins
Splicing
Mutations affecting splicing can cause genetic disease:cystic fibrosis retinitis pigmentosaspinal muscular atrophy Prader-Willi syndromeHuntington disease spinocerebellar ataxiamyotonic dystrophy Fragile-X syndrome
Or produce genetic susceptibility to disease:lupus bipolar disorderschizophrenia myocardial infarctiontype I diabetes asthmacardiac hypertrophy multiple sclerosisautoimmune diseases elevated cholesterol
Gene expression summary
Prokaryotes Eukaryotes
DNA
mRNA
directly translated(even before beingcompletely transcribed)
transcription
protein
cyto
pla
sm
DNA
pre-mRNA• capping• polyadenylation• splicing
transcription
mature mRNA
protein
• transport to cytoplasm• translation
cyto
pla
smnucl
eus
Quick review of protein structure amino acids
C CNH2
R
H
OH
O
generic amino acid
Quick review of protein structure side chain gives chemical properties
C CNH2
R
H
OH
O
Charged:Negative:
Polar, not charged:
Non-polar (hydrophobic):
Positive:
Quick review of protein structure polymer of amino acids = polypeptide ≈ protein
methionine aspartate
C CNH2
CH2
H
OH
O
CH2
S
CH3
C CNH2
CH2
H
OH
O
C
O
OH
C CNH3+
CH2
H
N
O
CH2
S
CH3
C C
CH2
H
OH
OH
C
O
OH
Quick review of protein structure polymer of amino acids = polypeptide ≈ protein