Biochemistry 3381A Study Guide - Quiz Guide: Mecp2, Genomic Imprinting, Dna Replication
27 May 2020
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Silencers: dna sequences that repress transcription of a gene (negative enhancers) Example: the nrse sequence (neutral restrictive silencer element) binds a transcription factor (nrsf) that is present in all tissues except adult neurons this binding prevents expression of typical neural proteins in non-neuronal tissue. Transcription factors have 3 major domains: dna-binding domain; trans-activating domain; protein-protein interaction domain. Recruitment of nucleosome modifying enzymes: histone acetyl/methyl transferases, histone deacetylases/demethylases. Stabilization of the transcription initiation complex pioneer transcription factors. In highly compacted (=repressed) chromatin it is difficult for many transcription factors to get access to their dna binding sites. Pioneer transcription factors are able to penetrate even highly condensed dna and allow other transcription factors access to their binding sites. Example: pbx works as pioneer transcription factor for the muscle-specific factor myod. ~ 5 % of the cytosines in mammalian dna are methylated. Dna methylation: long term stabilization of expression patterns. The degree of cytosine methylation can control the rate of transcription.
