MBB331_Week10-Fall-2011

Drosophila hsp70 drosophila promoter promoter gaga

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Unformatted text preview: transcription factors to gain access gain • eg. in vitro adenovirus promoter transcription: transcription: • (1) TFIID + RNAP II (& other general (1) factors) + histones --> transcribed transcribed • (2) histones + TFIID + RNAP II (& (2) other general factors) --> NOT transcribed Lewin Genes VII 2000 Oxford University Press 27 CHROMATIN & TRANSCRIPTION: CHROMATIN DYNAMIC MODEL DYNAMIC • Dynamic model: Dynamic transcription factor actively displaces nucleosomes using ATP hydrolysis hydrolysis • eg. Drosophila hsp70 Drosophila promoter: promoter: – GAGA transcription factor GAGA displaces nucleosomes in ATP-dependent manner ATP-dependent Lewin Genes VII 2000 Oxford University Press 28 CHROMATIN ASSEMBLY: TRANSCRIPTION • RNAP displaces DNA from RNAP octamer during transcription octamer • DNA behind RNAP loops forward DNA and octamer slides from DNA ahead of RNAP to DNA behind ahead • Octamer displaced by +ve DNA Octamer supercoiling ahead of moving RNAP RNAP • Octamer is displaced as intact Octamer unit - evidence: crosslinking evidence crosslinking histones together does not inhibit tran...
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