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A special sequence required for polyadenylation to occur
What is the significance of the “polyadenylation signal sequence”?
5’ -AAUAAA- 3’; located downstream from the stop codon
What is the polyadenylation signal sequence? Where is it located?
4 protein factors bind at/near signal sequence of pre-mRNA ~ 15 to 30 nt downstream; form cleavage and polyadenylation complexes.
What is step 1 of polyadenylation?
Pre-mRNA is cleaved, leaving PAP and CPSF at the 3’ end
What is step two of polyadenylation?
Poly (A) Polymerase (PAP)
Enzyme that catalyzes the addition of 20-200 adenine molecules to the 3’ end of cut Pre-mRNA
PABII Molecules
Poly A Binding protein II
3’ fragment is degraded in the nucleus
What is the third step of polyadenylation?
20-200 adenines added to 3’ end of cut Pre-mRNA via Poly (A) Polymerase
What is the fourth step of polyadenylation?
protecting mRNA from degradation
facilitating the transport of mRNA across the nuclear membrane and into the cytoplasm
Essential for binding to ribosomes
What are the 3 functions of polyadenylation?
CPSF
Cleavage-polyadenylation specificity factors
