Post-transcriptional Processing. Processing Events in Prokaryotes vs Eukaryotes.
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Transcript of Post-transcriptional Processing. Processing Events in Prokaryotes vs Eukaryotes.
![Page 1: Post-transcriptional Processing. Processing Events in Prokaryotes vs Eukaryotes.](https://reader035.fdocuments.net/reader035/viewer/2022070407/56649e425503460f94b352b3/html5/thumbnails/1.jpg)
Post-transcriptional Processing
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Processing Events in Prokaryotes vs
Eukaryotes
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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
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Cleavage and Polyadenylation
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Alternative pA Site Usage in Immunoglobulin Genes
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Pre-mRNA Splicing
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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
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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
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Association of snRNAs with Pre-mRNA
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Spliceosomal Complex
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Capping and Splicing Occur Co-transcriptionally
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Trans-Splicing in C. elegans
• Leader RNA is spliced onto 5' end of multiple pre-mRNAs
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Alternative Splicing Regulates Drosophila Sex Determination
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Other RNA Processing Events
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Ribosomal RNA Processing
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Small Nucleolar RNAs - snoRNAs
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Some Modified Bases Found in RNA