BIOL 202 Lecture Notes - Lecture 28: Covalent Bond, Radiography, Ester
5 Nov 2015
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closed dna: tightly packed nucleosomes o, associated with structural dnas and non-transcribed regions, e. g. centromere, telomeres, repetitive elements, euchromatin, loosely-packed nucleosomes o, associated with transcribed regions of chromosomes. open dna: any molecular processes that need to access dna (e. g. transcription, replication, and repair) have to unpack with nucleosomes. Transcriptional regulation by changes to chromatin structure: transcription factors recruit co-factors that can remodel or modify nucleosomes, chromatin remodelling (changes in chromatin architecture) Promoter is hidden, histone can compete with transcription factors. After remodeling, promoter is accessible - transcription can be activated. Discovery of chromatin remodeling complex in yeast: screen for mutant cells that cannot switch mating types (swi mutants, screen for mutant cells that cannot grow on sucrose: sugar non- fermenting (snf mutants) Large multiprotein complex (9 proteins) that does not bind dna. Uses energy from atp to move nucleosomes (no covalent modification or histones: post-translational (covalent modification) of histone tails (e. g. acetylation and methylation)
