transcription Regulation Extra slides

transcription Regulation Extra slides - Transcription...

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Transcription Termination Chain Termination 1.Rho ( ρ ) Dependent termination. 2.Rho ( ρ ) Independent termination. Two mechanisms 1) Rho - the termination factor protein – Rho is an ATP-dependent helicase – it moves along the RNA transcript, finds the "bubble", unwinds it and releases the RNA chain. Chain Termination
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Rho-Dependent Transcription Termination (depends on a protein AND a DNA sequence) G/C -rich site RNAP slows down Rho helicase catches up Elongating complex is disrupted
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Two mechanisms 2) Rho-Independent - termination sites in DNA – inverted repeat, rich in G:C, which forms a stem-loop in RNA transcript – 6-8 A’s in DNA coding for U’s in transcript Chain Termination
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Rho-Independent Transcription Termination (depends on DNA sequence - NOT a protein factor) Stem-loop structure
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Rho independent termination RNAP pauses when it reaches a termination site. The pause may give the hairpin structure time to fold The fold disrupts important interactions between the RNAP and its RNA product The U-rich RNA can dissociate from the template The complex is now disrupted and elongation is terminated
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Gilmour D S , Fan R J. Biol. Chem. 2008;283:661-664
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• There are many ways to regulate transcriptional: Use of alternate sigma factors • Positive control, in which a regulatory protein acts as an activator , stimulating transcription; • Negative control in which expression is controlled by a repressor that inhibits transcription. Gene Regulation in Bacteria 1. Alternate sigma factor usage : controls selective transcription of entire sets of genes σ 32 σ 60 vegetative (principal) heat shock nitrogen starvation σ 70 TTGACA TATAAT (16-19 bp) (5-9 bp) A +1 CNCTTGA CCCATNT (13-15 bp) (5-9 bp) A +1 CTGGNA TTGCA (6 bp) (5-9 bp) A +1 Ways to Regulate Transcription
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2. Positive Regulation (activation): a positive regulatory factor (activator) improves the ability of RNAP to bind to and initiate transcription at a weak promoter.
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This note was uploaded on 03/16/2010 for the course BIO 362 taught by Professor Walikarzai during the Spring '10 term at SUNY Stony Brook.

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transcription Regulation Extra slides - Transcription...

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