POST TRANSCRIPTIONAL CONTROL Flashcards
What are the functions of RNA capping?
Stabilizes RNS and protect from 5’ to 3’ degradation
Enhances translation
facilitates and mediates nuclear transport
mediates the splicing of the first intron
Whatis mRNA processing?
It is the removal of introns from a pre-mRNA to form mature mRNA
What are introns?
Portion of pre-mRNA that is removed via splicing and not found in mature mRNA
What are exons?
The coding sequemce found in mature mRNA
The splice sites are found where?
At the intro/exon junction
What are the non coding exons called?
Whaere are they found?
Untranslated region (UTR)
At 5’ and 3’ ends
UTRs may contain what? Give an example
Regulatory sequences i.e polyadenylation site at 3’ UTR
Name and describe the steps of maturation of mRNA
1) Capping at the 5’ end: Stabilizes, protects, enhances translation, nuclear transportation and splicing of first intron
2) Splicing: removal of introns
3) 3’ end processing: cleavage and polyadenylation of polyA site.
What are the sequences that defines an intron?
5’ (donor) site - GU
3’ (acceptor) site - AG
Branchpoint or branch site - A
What is found btw the branchpoint and the 3’ splice site?
Polypyrimidine stretch containing many Cs and Us
In a splicing rxn, bond btw what and what is first broken?
Btw the G of the 5’ splice site and exon 1
The broken off G combines with the branchpoint and together form what?
Intron Lariat
The bond btw - and - in the second step of splicing is broken and the third step is what?
G of the 3’ splicing site and exon 2 is broken
The two exons are joined and the intron is discarded.
Where does splicing take place?
In spliceosomes
S spliceosome is composed of what?
Pre-mRNA in its various splicing stages, snRNPs and other factors that catalyze splicing rxn.
