Ahexamercontainingsixidenticalunitswhichbindtherutsite

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Unformatted text preview: RNA polymerase holoenzyme Ensures transcription starts at promoter sites only. Transcription Elongation: Prokaryotes Transcription bubble RNA­DNA hybrid Transcription Termination Transcription Termination Prokaryotes: Intrinsic termination • Termination sequence is – 40 bases ends in a GC­rich stretch followed by six or more AAAs. • GC­rich stretch forms hairpin loop. • A­T RNA­DNA hybrids are weak • causing the RNA polymerase to backtrack in an attempt to stabilize hybrid. • Encounters the hairpin loop formed by the GC­rich region • falls off. Transcription Termination Transcription Termination Prokaryotes: Rho­Dependent Termination • Involves the rho factor. – A hexamer containing six identical units which bind the rut site. • A rho utilization site = rut. • Termination sequence is 40­60 bases which is rich in C residues and poor in G residues. • Rut is located in the upstream part of this region which is an RNA polymerase ‘pause’ site. • During termination – – – 1) rho binds to rut 2) RNA polymerase pauses 3) rho dissociates the polymerase from RNA. Transcription initiation: Transcription initiation: Eukaryotes RNA Processing RNA Processing Eukaryotes RNA Processing RNA Processing Eukaryotes RNA Processing RNA Processing Eukaryotes Splicing: How it works Splicing: How it w...
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