01:694:215 Lecture Notes - Lecture 3: Histidine, Plasmid, His3
26 Mar 2018
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Document Summary
Chromatin- dna plus tightly associated proteins (including histones) that fold or condense dna. Dna wraps around histones tight loops called nucleosome. Histone acetylases and deacetylases provide a critical link between chromatin structure and transcriptional output. Acetylation adds o group making dna more negative. Gcn5 adds more acetyl groups to the nucleosomes, allowing histones to break away and polymerase to attach to the promoter region. Activator hyperacetylation more negative histones break away transcription. Repression deacetylation more positive histones tightly bound no transcription (repression/silencing) Prevent other proteins from attaching to dna. Sir2 = hdac: deacetylases turns off transcription. Complex spreads down the dna after deacetylating each histone. Trp- tryptophan turns the promoter on and off. Insert trp1 inside the promoter (which is silenced) If inserted in a mutant sir2, then silencing will not occur and trp1 gene can make tryptophan and transcription can occur. Sir2 (j)- wild type turns trp off small white (wild type)
