HMB321H1 Lecture Notes - Lecture 15: Cpg Site, Histone Methylation, Methyl Group
8 Oct 2011
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Modi cations are heritable, e. g. imprinting -- without change to the dna (just additive funct"al groups) Can include methylation, histone deacetylation, which interfere with transcription. Usually occur at the cpg island site (c-phosphate-g) Cpg islands are high concentrations of cpg sequences; usually near gene promoters. Lots of methylation can be incurred to turn genes off effectively. Methylation at cpg => cytosine changes to 5-methylcytosine, which is not readable. Transcriptionally active chromatin => unmethylated; acetylated (allows euchromatin transcr) Transcriptionally competent chromatin => still transcribed because of acetylated, despite methylation on gene. Addition of acetyl group causes difference in transcriptional ability. Deacetylation inactivates chromatin transcription (even more so with methylation) Ways to modify histone via addition of phosphate group to serine molecule. Can reduce ability of histone to bind dna to inhibit transcription. Addition of methyl to amino acids in r or k in histone tails (happens on actual protein) Alters the readability of the dna bound by those histones.
