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Promoter sequences from 10 bacteriophage and bacterial genes

Promoter sequences from 10 bacteriophage and bacterial genes. Figure 10-13 Catabolite control of the lac operon. (a) Only under conditions of low glucose is adenylate cyclase active and cAMP (cyclic adenosine monophosphate) formed. (b) When cAMP is present, it forms a complex with CAP

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Promoter sequences from 10 bacteriophage and bacterial genes

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  1. Promoter sequences from 10 bacteriophage and bacterial genes

  2. Figure 10-13 Catabolite control of the lac operon. (a) Only under conditions of low glucose is adenylate cyclase active and cAMP (cyclic adenosine monophosphate) formed. (b) When cAMP is present, it forms a complex with CAP (catabolite activator protein) that activates transcription by binding to a region within the lac promoter.

  3. NEGATIVE REGULATION REPRESSIBLE TRANSCRIPTION THE trp OPERON Aporepressor Operator Co-repressor Active repressor X

  4. 1 2 3 4 1 2 3 4

  5. RNA Polymerase Transcribing a Prokaryotic Gene • Initiation occurs at a transcription start site in a promoter (DNA sequence) • Termination occurs at a transcription stop site • Activation of bacterial RNA polymerase requires binding of sigma factor

  6. Transcription in Eukaryotes Eukaryotic RNA Polymerases • Three different RNA polymerases transcribe nuclear genes • Other RNA polymerases found in mitochondria and chloroplasts

  7. Eukaryotic vs. Prokaryotic Transcription • In eukaryotes, transcription and translation occur in separate compartments. • In bacteria, mRNA is polycistronic; in eukaryotes, mRNA is usually monocistronic. • Polycistronic: one mRNA codes for more than one polypeptide • moncistronic: one mRNA codes for only one polypeptide • 3 RNA polymerases in euk., 1 in prok. • Binding of Basal Transcription Factors required for euk. RNA Pol II binding. • “Processing” of mRNA in eukaryotes, no processing in prokaryotes

  8. Gene expression

  9. TERMINATION • RNA polymerase meets the terminator • Terminator sequence: AAUAAA • RNA polymerase releases from DNA • Prokaryotes-releases at termination signal • Eukaryotes-releases 10-35 base pairs after termination signal

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