BIOL308 Lecture Notes - Rna Polymerase Ii, Dna Methyltransferase, Methyltransferase
16 Jul 2014
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Document Summary
Deficiency of cg pairs in genome in general (ave 40%) Mostly present in some promoters: cpg boxes or islands. Methyl groups are attached to c in some cg doublets on dna. Elimination of methylated c during evolution through conversion into t. Deamination of normal c: repair system thinks its u, not present in dna, mutation is recognized; gets repaired. Deamination of methylated c: repair system thinks its t, present in dna, mutation is not recognized for repair; it stays. Methylation of c in cpg doublets prevents transcription in general: Both dna and histones can be methylated: generally a sign of inactive chromatin heterochromatin. Methylated cpgs: recognize by methyl-binding domain proteins (mbp) that can recruit histone- modification enzymes such as histone deacetylase (hdac) and histone methyl transferase (hmt) Histone deacetylation and methylaton: local chromatin will be condensed. Extensive methylation near (or in) a gene sequence generally prevents (or stops) transcription of that gene.
