lecturenoteschap21-10-2slides

lecturenoteschap21-10-2slides - BCMB 3100 - Chapter 21...

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1 BCMB 3100 - Chapter 21 Transcription & RNA Processing Definition of gene RNA Polymerase Gene coding vs template strand Promoter Transcription in E. col Transcription in E. coli Transcription factors mRNA processing Biological information flow
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2 _______ - a DNA sequence that is transcribed (includes genes that do not encode proteins encode proteins) ______________________ ” encode proteins or RNA essential for normal activities of the cell (e.g. enzymes in basic activities of the cell (e.g. enzymes in basic metabolic pathways, tRNAs and rRNAs) Four Classes of RNA in living organisms ( review ) Messenger RNA ( mRNA ) - linear “copies” of DNA that encode genetic information. Encode primary structure of protein. ~1-3% of total RNA, relatively unstable (discovered by Jacob & Monod). Non coding RNA Non-coding RNA Ribosomal RNA ( rRNA ) - ~80% of total RNA, part of ribosomes (translation machinery) Transfer RNA ( tRNA ) - ~15% of total RNA, 73-95 nucleotides long, carry activated amino acids to ribosomes during translation (S ll RNA h tlt i t ii t d / it i th (Small RNA) - may have catalytic activity and/or associate with proteins to enhance activity, some involved with RNA processing (includes snRNA and microRNA, the latter involved in mRNA degradation, translation inhibition and chromatin remodeling), (long non-coding RNAs (long ncRNAs)): functions being determined.
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3 RNA Synthesis ( E.coli ) Transcription DNA  RNA RNA Polymerase (450 kd) (1960, Hurwitz; Weiss) (recognizes promoter & (binds DNA template) & initiates synthesis) 2   (holoenzyme) forms phosphodiester bond binds rNTPs 2  (core enzyme) (see Table 21.2 & Fig. 21.2) RNA Synthesis 1) Intiation RNA polymerase is responsible for these 2) Elongation 3) Termination responsible for these function in RNA synthesis E. coli RNA polymerase synthesizes all major types of RNA: mRNA, tRNA, rRNA, small RNA
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4 Transcription in E.coli 1) RNA polymerase searches for initiation sites (~2000 in 4,000,000 bp) 2) Unwinds DNA to produce single-stranded template 3) Selects correct ribonucleotide and catalyzes the formation of phosphodiester bonds (totally processive) 4) Detects termination signals 5) Interacts with activators & repressor proteins DNA template RNA polymerase Requirements for Transcription Note: RNA Polymerase does Transcription factors NTPs (ATP,CTP,GTP,UTP) Mg ++ NOT require a primer. RNA chains can be initiated de novo. Mechanism of elongation is the same as for DNA Polymerase: nucleophilic attack by 3’-OH on - phosphate of NTP
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5 Fig 21.3 • RNA polymerase reaction Fig 21.3 (cont) E.coli transcription rate: 30-85 nucleotides/se nucleotides/sec Error rate = 10 -6 RNA Polymerase has no exonuclease activity
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6 Fig 21.5
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This note was uploaded on 12/03/2011 for the course CHEM 3100 taught by Professor Dervartanian during the Fall '09 term at University of Georgia Athens.

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lecturenoteschap21-10-2slides - BCMB 3100 - Chapter 21...

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