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Post-transcriptional Processing. Processing Events in Prokaryotes vs Eukaryotes. Capping. RNA Stability 5'-5' linkage not recognized by RNAses Methylation of 2'OH prevents use of the hydroxyl by RNAses Translation efficiency CAP binding factor part of translation initiation – eIF4E.
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Capping • RNA Stability • 5'-5' linkage not recognized by RNAses • Methylation of 2'OH prevents use of the hydroxyl by RNAses • Translation efficiency • CAP binding factor part of translation initiation – eIF4E Triphosphatase Guanysyl transferase Guanosine-7-methyl transferase 2'-O-methyl transferase 2'-O-methyl transferase
snRNAs & snRNPs: The Splice Girls • U1 snRNA • U2 snRNA • U4 snRNA • U5 snRNA • U6 snRNA • U1 snRNP* • U2 snRNP • U4 snRNP • U5 snRNP • U6 snRNP snRNAs associated with various numbers of proteins to form small nuclear ribonucleoprotein complexes * Pronounced snurps
Splicing • U1 snRNP • Recognition of 5’ splice site • Interaction with U6 snRNP • U2 snRNP • Recognition of branch point sequences • Base pairs with U6 snRNP • U4 snRNP • Base pairs with U6 & U5 snRNPs to recruit them to spliceosome • U5 snRNP • Recognizes last nt in intron & first nucleotide in exon sequences • U6 snRNP • Displaces U1 at 5' site while base pairing with U2 • Positions 5' site near branch point
Trans-Splicing in C. elegans • Leader RNA is spliced onto 5' end of multiple pre-mRNAs