BIOL 205 Lecture Notes - Group Ii Intron, Thomas Cech, Transesterification
22 Nov 2013
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Group i: e. g. tetrahymena rrna (tom cech) no sequence conservation at splice junction carry conserved sequences internally introns self-splice: guanosine as cofactor (rna catalysis, ribozymes) transesterifications, no external energy input. Pocket created to hold guanosine residue (green g?) Internal guide sequence: rna has an internal guide to help fold intron close to reactive guanosine. Group i introns can be converted to ribozymes companies: Good way of targeting destruction of rna. But didn"t really work well and rnai came in and replaced all that technology. Splicesome-mediated splicing: gu found at 5" intron-exon junction, g marks 3" intron-exon junction, a is part of branch site (consensus longer than this, no particular order in which introns are removed. Complex patterns of eukaryotic mrna splicing tropomyosin gene. 2" hydroxyl of intron attacks phosphate of exon (1st transesterification) Then 3" hydroxyl attacks 5" phosphate of other exons (2nd transesterification) And 5"-2" linkage created in lariat intron. Contain u1 or u2 small nuclear rna (snrna)
