BCHM 4116 1st Edition Lecture 23Outline of Last Lecture I. MutationsOutline of Current Lecture I. Genes Transcribed of Gene Expression II. Transcription has 4 stages Current LectureChapter 29: Transcription and Regulation of Gene Expression1. 29.1 – Genes Transcribed in Prokaryotes a. RNA poli.α2ββ ' σii.β β' = 2 large subunits1. performs most of enzymatic function iii. Binding of σ - subunit recognizes diff. DNA sequences that act as promoters1. Promoters = identify transcription start site b. Transcription has 4 stagesi. Binding of RNA pol at promter site1.σ – subunit recognizes promoter sequence2.RNA pol∧ promter form a complex3. AKA “closed” promoter complex b/c dsDNA is not “opened” 4. +1 = transcription start site 5. within promoter are 2 consensus sequencesa. Pribnow box -10 region i. TATAATb. -35 region 6.σ – subunit recognizes and binds to -10 & -35 regions ii. Initiation of polymerization1. RNA pol does not require primer 2.σ – subunit dissociates from RNA pol once 9-12 resides long has been formed = completion of initiation 3.core RNA pol = highly processive and goes on to synthesize remainder of mRNAiii. Chain elongationThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.1. Catalyzed by core polymerase 2. To prevent torsional stress from inhibiting transcription, gyrase introduces negative supercoils (& thereby remove positive supercoils) ahead of RNA pol3. Topoisomerase removes negative supercoil behind DNA iv. Chain termination 1. Bacteriaa. Intrinsic terminationi. Specific sequences in DNA called termination sites 1. Inverted repeats, typically G-C rich, so forms stem-loop structure 2. Nonrepeating segment that punctuates invertedrepeats3. 6-8 A’s in DNA, coding for U’s in transcriptb. Rho factori. Less common & mechanistically more complexii. ATP-dependent hexameric helicaseiii. Catalyzes unwinding of RNA:DNA duplexiv. Rho factor recognizes and binds to C-rich region , then advances in 5’3’ direction until reaches transcription bubble v. There it catalyzes unwinding of transcript and template, releasing RNA
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