Chapter_29

Chapter_29 - Chapter 29 RNA Synthesis (Transcription) and...

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Chapter 29 RNA Synthesis (Transcription) and Splicing Transcription in Prokaryotes: promoters, RNA polymerase, termination Eukaryotic transcription: transcription factors in initiation and capping in termination RNA processing: spliceosomes, snRNPs, and RNA self splicing
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Importance of RNA Editing and Splicing 15% of genetic diseases have splicing defects Regulation of gene expression through splicing RNA editing 100,000 genes expected: 25,000 found-does RNA editing allow for more than one protein from each gene?
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The Role of Non-Coding RNA Hütenhofer et al, TIGS, 2005 ENCODE project 2007: 93% of genome in some cells may be transcribed Birney et al Nature 2007
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Transcription in Prokaryotes and in Eukaryotes Initiation 2000 sites on 4.8 million bps ( E. Coli ) (cis-acting elements) Elongation Unwinds DNA forms phosphodiester bonds (processive) Termination Distinct termination signals Basic steps apply to all RNA synthesis (mRNA, tRNA, & rRNA)
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RNA and DNA Polymerase Represent an Example of Convergent Evolution The reaction and the catalytic site are similar The overall structure and subunit configuration differ 400kd, 4 types of subunits σ subunit finds promoter, then dissociates α2ββ σ is the “core” enzyme All forms of RNA (mRNA, tRNA, rRNA) are transcribed by the same mechanisms 1 Mg comes in with NTP and leaves with PPi
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DNA Promoters Direct the Start of Transcription Footprinting maps the binding site of RNA polymerase Coding strand = (+) sense Template strand = (-) antisense Promoter strength is correlated with similarity to consensus sequence TTGACA TATAAT Start site +1 -10 -35 5’
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Recognition of the Promoter Site by the σ Subunit of RNA Pol RNA polymerase has non-specific DNA binding activity σ subunit 1) reduces non-specific binding 2) increases affinity for -10 region 3) dissociates and binds another polymerase Binding rate is 1010 M-1s-1 (100 times faster than 3-dimensional diffusion) σ32 directs RNA Pol to the heat- shock promoter & σ54 to the nitrogen- starvation promoter
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Chapter_29 - Chapter 29 RNA Synthesis (Transcription) and...

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