Biology And Biomedical Sciences BIOL 2960 Lecture Notes - Lecture 30: Transcription Factor Ii B, Helicase, Transcription Factor Ii H
13 Dec 2016
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Lecture 30: chromatin and eukaryotic initiation of transcription. A narrowed minor groove at sites of interaction favors a/t base pairs. Implication- sequence specific positioning of nucleosomes on dna: dna is slightly underwound (~10. 2 bp / turn compared to canonical b-dna) The ramp is not perfect: histone modification, histone amino-terminal tails are conserved (but aren"t part of the core, histone n-terminal tails are targets for covalent modifications that regulate chromatin structure and provide binding sites for proteins. Play an important role in higher order chromatin structure/packing: dna is acidic because of negatively charged phosphates, histones are basic because of abundant positively charged aa residues (lysine and arginine) Lysine in n-terminal tails can be modified by acetylation which can neutralize the positive charge: the n-terminal tails of histones are targets of extensive modifications: Methylation (ie- lysine 4, 9, 27), often serve as binding sites for proteins.
