Class 9 Slides

mRNA processing in eukaryotes important for

mRNA stability

mRNA processing in eukaryotes occurs when/where

Occurs in nucleus:

• Same place as transcription

• Same time as transcription

mRNA processing in eukaryotes, what is involved

Complexes responsible for processing associate with the CTD of RNA Pol II

Capping proteins bind to phospho-Ser5 CTD

Spliceosomes associate with phospho-Ser5,phospho-Ser2 CTD

End cleavage proteins associate with CTD that has lost some Ser5 phosphorylation

mRNA processing in eukaryotes locations, what are they based on

Locations of processing events are determined by the sequence of the mRNA and the binding of proteins and complexes that do the processing

5’ end is structurally distinct from other nucleic acids and ends

Splice sites have specific sequences (and surrounding sequences)

mRNA is cleaved at AAUAAA, then polyadenylated at 3’ end

Constitutive splicing is

the process of intron removal and exon ligation of the majority of the exons in the order in which they appear in a gene. Alternative splicing is a deviation from this preferred sequence where certain exons are skipped resulting in various forms of mature mRNA.

Splicing, what does it, what is needed for it

Introns are removed by the spliceosome

Exons are joined together to form the mature mRNA sequence

Each splicing event requires a 5’ splice site, a 3’ splice site, and a branchpoint A in the intron

These are encoded in the gene and part of the mRNA sequence when it is transcribed