Ch. 17c RNA Processing & Transcription Regulation (Exam 2) Flashcards
What does post-transcriptional gene control mean?
All processes regulating gene expression after the start of transcription
What are the 3 main processes of pre-mRNA processing?
1) 5’ capping
2) Polyadenylation
3) Intron splicing
What is a 5’ cap?
Modification of the 5’ on the primary transcript (pre-mRNA)
What does a 5’ cap create?
7-methylguanylate (m7Gppp) attached to the first nucleotide of the pre-mRNA
How does m7Gppp link to the first nucleotide of pre-mRNA?
5’-5’ linkage that links the 5’C of one pentose to another
What are 3 purposes of the 5’ cap?
1) Transport of mRNA to cytoplasm
2) Protect against nuclease
3) Start translation
M7Gppp is an example of a…
Nucleoside triphosphate
What 4 things does the 5’ cap structure influence in mRNA?
1) Stability
2) Splicing
3) Export
4) Translation
Pre-mRNA is the primary transcript with the same organization as…
The gene
What is splicing?
Removal of introns to turn pre-mRNA into mature mRNA
What is the purpose of the pre-mRNA splice sites?
To help direct splicing reactions
Where is the 5’ splice site?
On the 5’, left end of the intron
What consensus sequence does the 5’ splice site include (HINT: 2 nucleotide bases)?
GU
Where is the 3’ splice site?
On the 3’, left end of the intron
What consensus sequence does the 3’ splice site include?
AG
Is the central region of the intron important for splicing?
Generally, no
What does the GU-AG rule describe?
The requirement of these dinucleotides at the 5’ and 3’ splice sites respectively so that they come together after splicing
What 3 things does splicing require?
1) 5’ splice site
2) 3’ splice site
3) Branch site
What is the purpose of the branch site?
To initiate a nucleophilic attack on the 5’ splice site
Splicing requires 2 { } reactions.
Transesterification