DNA-transcription@生物化学精品.pptx

DNA Transcription;DNA Transcription;Central Dogma;Coding strand, Sense strand, Crick strand;Bacterial RNA Polymerase ;DNA-Dependent RNA Polymerases (RNAP);Differences between DNAP and RNAP;Structure and Function of the RNAP in Prokaryotes;a a2 a2b a2bb’ = core enzyme;a1;The sigma subunit ;E.?coli also has six alternative sigma factors that are used in special circumstances ;Some of the sigma factors found in Bacillus subtilis ;Anti-sigma factors;RNAP core structure from T. aquaticus.;;RNAP II Inhibitor;The chemical structure of α-amanitin;RNAPs in Eukaryotes;;(PNAS January 30, 2001 98, 892-897);RNA Polymerase II ;Important feature of RPB1 ;;RNA Polymerase II ;Viral RNA Polymerases;Fig. 1 Structure of transcribing T7 RNA polymerase;Detailed Transcriptional Mechanism;Prokaryotic DNA Transcription;;;;;;Properties of Promoters ;Important Promoter Features (tested by mutations) ;Binding of RNAP to Template DNA;;Transcriptional regulation in bacteria;DNA wrapping model (B. Coulombe);Finding and binding the promoter;Transcriptional regulation in bacteria;Transcriptional regulation in bacteria;Chain Elongation ;Science, vol. 281, p 424 (1998);;Two mechanisms Rho(ρ) - the termination factor protein rho is an ATP-dependent helicase it moves along RNA transcript, finds the bubble, unwinds it and releases RNA chain Specific sequences - termination sites in DNA inverted repeat, rich in G:C, which forms a stem-loop in RNA transcript 6-8 As in DNA coding for Us in transcript ;Rho-independent transcription termination (depends on DNA sequence - NOT a protein factor);Rho-independent transcription termination;;Differences Transcription Bacteria vs. Eukaryotes;Enhancers can occur in a variety of positions with respect to genes;Trans-acting factor;Other Cis-acting Elements;DNA transcription by RNAP I;;DNA transcription by RNAP III;;DNA transcription by RNAP II;Enkaryotic Promoter;An Analogy;RNAP I, II AND III Promoters;;;Relative positions of GTFs and RNAP II on D