Date post: | 11-Jan-2016 |
Category: |
Documents |
Upload: | roger-jenkins |
View: | 215 times |
Download: | 0 times |
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
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