BCH 3170 Lecture Notes - Lecture 18: Cpg Site, Histone Code, Histone Deacetylase
2 Mar 2016
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Cannot methylate de novo (from nothing) it can only come in and fill the gap. Dna methylation occurs when a cytosine is adjacent 5" to a guanine, called a. Around 70% of all cpgs are methylated. Non-symmetrical methylation can occur for other sequences. Human genome is not methylated uniformly because the cpg dinucleotide are not distributed regularly in the genome. Most cpg are found in clusters called cpg islands or cgi stretches of 100 to. About 50% of genes contain cgis close to their transcription start site. Methylation of a promoter is a way to regulate expression of a gene. Unmethylated cg-rich islands close to the promoter region of eukaryotic housekeeping genes. Housekeeping genes are always on and working. Methylation of cpg islands is believe to regulate gene expression bindng of activator rdbps and anchoring of the transcription machinery on an active promoter has the effect of preventing recruitment of dna methyltransferase.
