生物化学讲义chaptercompleternametabolism.pptxVIP

Chapter 26 RNA Metabolism;1. RNA molecules have great structural and functional diversity;2. DNA and RNA syntheses are similar in some aspects but different in others;3. The multimeric RNA polymerase in E.coli has multiple functions;The E. coli RNA polymerase holoenzyme consists of six subunits: a2bb’? s.;4. RNA synthesis occurs in a “moving” transcription bubble on the DNA template;5. RNA polymerase recognizes specific promoter sequences on DNA to initiate transcription;The footprinting technique;;;An actual footprinting result (RNA polymerase binding to a lac promoter);Alignment of different promoter sequences from E.coli genes: the –10 (the Pribnow box) and –35 consensus region were revealed.;Promoter of E.coli Add gene;6. The s subunits enable the E.coli RNA polymerase to recognize specific promoter sites;Standard Heat-shock Nitrogen starvation;7. RNA polymerase unwinds the template DNA then initiate RNA synthesis;8. E.coli RNA polymerase stops synthesizing RNA at specific terminator DNA sequences;The r-dependent terminator DNA exhibit no obvious sequence similarities (probably the RNA polymerase detects noncontiguous structural features?). The r-dependent terminator is more often found in phages (where it was originally discovered), but rarely in E.coli. In contrast to what was originally expected, the active signals for stopping RNA synthesis in both r-independent and r-dependent transcription terminators lie in the newly synthesized RNA rather than in the DNA template. ;r-independent terminator: a model;Transcription terminator of E.coli Add gene;Model for an r-dependent terminator;9. Transcription is a highly regulated process;10. Three kinds of RNA polymerases (I, II, and III) have been revealed for making RNAs in the nuclears of eukaryotic cells;Eukaryotic RNA polymerases;11. RNA polymerase II (Pol II) binds to promoters of thousands of protein-coding genes;General features of promoters for protein-coding genes in higher eukaryotes;12. Pol II