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 Triphosphatase Guanysyl transferase Guanosine- 7-methyl transferase 2'-O-methyl transferase

Cleavage and Polyadenylation

Alternative pA Site Usage in Immunoglobulin Genes

Pre-mRNA Splicing

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

Association of snRNAs with Pre- mRNA

Spliceosomal Complex

Capping and Splicing Occur Co-transcriptionally

Trans-Splicing in C. elegans Leader RNA is spliced onto 5' end of multiple pre-mRNAs

Alternative Splicing Regulates Drosophila Sex Determination

Other RNA Processing Events

Ribosomal RNA Processing

Small Nucleolar RNAs - snoRNAs

Some Modified Bases Found in RNA