LIFESCI 3 Study Guide - Final Guide: Polyadenylation, Guanine, Intron
Document Summary
Processing & termination newly synthesized rna needs to be processed before nuclear export & translation. After promoter escape, capping enzymes are recruited. Capping enzymes add 5" cap to the end of mrna to prevent degradation. Added to 5" end of rna transcript. Need to know this about 5" cap: Mrnas are capped as it emerges from rna exit channel of pol ii. 5" cap is important in binding mrna to ribosome for translation. After capping, phosphorylation pattern of pol ii ctd tail allowing for promoter escape signals splicing machinery to come in. Splicing machinery is signaled by promoter escape after capping occurs. Polyadenylation: cleaving mrna to add poly-a tail. 2 protein complexes recruited to ctd near end of transcription. When pol ii transcribed a poly-a signal sequence, mrna gets cleaved. Poly-a polymerase (pap) recruited adds 200 adenines to 3" end of rna transcript. Does not need a template for synthesis.
