BIOL308 Study Guide - Alternative Splicing, Adenine, Tryptophan
8 Dec 2013
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Study questions: lec 24-29: describe the role of histone acetylation/deacetylation in regulation of transcription. The n terminal end of histones contain positive lysine groups that tightly bond with dna and can either acteylate or deacetylate the histones. When acetylated, the positive charge on lysine is neutralized and eliminates interactions with dna; chromatin is less condensed chromatin (euchromatin)and the promoter regions are accessible for transcription. The acetylation is catalyzed by histone acetyltransferases, also called hats and this leads to activation of gene expression. Deacetylation (catalysed by deacetylases) increases the positive charge on the lysine residues leading to lesser repulsion between the dna strands and therefore, a more condensed heterochromatin structure. Binding sites are now inaccessible for tfs and transcription is inhibited and this leads to repression of gene activity: describe the role of chromatin remodelling complexes in regulation of transcription. Histone acetylation isn"t sufficient for activation; nucleosomes are still intact and have to be repositioned to expose the promoter elements.
