Lecture 3 - 4 - RNA Processing

Lecture 3 - 4 - RNA Processing - RNA Processing The CTD of...

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RNA Processing The CTD of large subunit in RNAP II Is unique among RNAPs YSPTSPS(52) in humans YSPTSPS(26) in yeast The 5 S is initially phosphorylated, followed by the 2 S Pre-mRNA is modified as it emerges because of its instability - 7’ methylguanylate CAP is added to the 5’ terminal nucleotide through an unusual 5’-5’ linkage - animal cells and in higher plants the 2’ hydroxyl of the ribose group of the first base is methylated - vertebrates, the second base is also methylated CAP protects the pre-mRNA from enzymatic degradation, while facilitating nuclear export and recognition by translation initiation factors - Most eukaryotic genes have introns, more and more common in higher organisms - Introns are not junk, they code regulatory information Discovered based on discrepancy between mRNA size and gene size Discovered via hybridization experiments where mRNA were annealed to their coding DNA in the genome (introns loop out with no hybrid partner in the mRNA) Analysis of a large number of introns reveals that their border sequences are conserved - Useful features for in silico prediction of mRNA sequences based off DNA GU --- --- --- A ---AG (The GU,AG rule, with the A of the branch point also conserved) - hydroxyl group branch point residue attacks the 5’ phosphate
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This note was uploaded on 04/22/2008 for the course BIOL 200 taught by Professor Bureau during the Fall '06 term at McGill.

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Lecture 3 - 4 - RNA Processing - RNA Processing The CTD of...

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