MBB 222 Lecture Notes - Lecture 30: Rna Polymerase Ii, Precursor Mrna, Polyadenylation
20 Dec 2018
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Document Summary
Rna processing pre-mrna acquires a 5" cap, a 3" poly-a tail, and is spliced as it is processed into mrna. Almost all eukaryotic mrnas are capped the guanine is subsequently methylated at n-7 7-methylguanosine (7-methyl g) 5" cap is added early on, before synthesis of the primary mrna transcript is complete. Only added to rna polymerase ii (mrna) transcripts cap participates in binding of mrna to ribosome to initiate protein synthesis. May also stabilize mrna by protecting it from nucleases. Mrna processing enzymes are associated with the ctd of rna polymerase ii. Allows processing to occur as the transcript is being synthesized. Different processing enzymes bind to the ctd depending on its phosphorylation state. Ii: the endonuclease cleaves the transcript 10 30 bases downstream from (i. e. , 3" of) aauaaa, releasing it from rnap ii, the polyadenylate polymerase adds 80-250 a residues.
