PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10The s Subunit Recognizes and Binds to the PromoterSlide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Higher Organisms have more Introns. More introns means more opportunities for alternative splicing.Slide 40Slide 41Slide 42Slide 43Lecture 23 - Chapter 36Transcription and the Regulation of Gene ExpressionLecture 23 - Chapter 36Transcription and the Regulation of Gene ExpressionOutlineOutline•Transcription in prokaryotes•RNA polymerase•Sites of Initiation•Transcription Elongation•Transcription termination•Transcription Regulation- the lac operon•Overview of Transcription in Eukaryotes•Transcription in prokaryotes•RNA polymerase•Sites of Initiation•Transcription Elongation•Transcription termination•Transcription Regulation- the lac operon•Overview of Transcription in EukaryotesDNA rRNA mRNA tRNA ProteinTRANSCRIPTIONbyRNA Polymerase (DNA-dependent)TRANSCRIPTIONbyRNA Polymerase (DNA-dependent)TRANSLATIONonRibosomeTRANSLATIONonRibosomeThe RNAsThe RNAsBut, unlike mRNAs, rRNAs and tRNAs are not subsequently translated into proteinsBut, unlike mRNAs, rRNAs and tRNAs are not subsequently translated into proteinsmRNA, rRNA and tRNA are all synthesized by transcription of DNA sequences.mRNA, rRNA and tRNA are all synthesized by transcription of DNA sequences.Telomerase RNATelomerase RNAExpression of Genetic InformationExpression of Genetic InformationRequires Mg2+ or Mn2+Requires Mg2+ or Mn2+mRNAReplicationDNA DNAProkaryotic Molecular BiologyProkaryotic Molecular Biology5’-N’-Initiation site on DNAmRNA 2mRNA 1mRNA 3mRNA 4In Prokaryotes Transcription and Translation are CoupledIn Prokaryotes Transcription and Translation are CoupledmRNA/transcriptmRNA/transcriptProkaryotic mRNAProkaryotic mRNAPolycistronic mRNA Polycistronic mRNA DNADNAProtein AProtein AProtein BProtein BProtein cProtein cCore Polymerase 2’Holoenzyme CoreCore Polymerase 2’Holoenzyme CoreCore Bacterial RNA PolymeraseCore Bacterial RNA PolymeraseSubunits of E. coli RNA polymeraseSubunits of E. coli RNA polymeraseThe three stages of RNA synthesis are:The three stages of RNA synthesis are:1. Initiation2. Elongation3. Termination1. Initiation2. Elongation3. TerminationThe Subunit Recognizes and Binds to the PromoterThe Subunit Recognizes and Binds to the PromoterStart site-10-35+1ConsensusConsensusTTGACATATAAT17+/- 25’--3’The E coli RNA polymerase holoenzymeThe E coli RNA polymerase holoenzymeTranscription InitiationTranscription InitiationPribnow boxPribnow box-35 sequence-35 sequence~17 bp~17 bpNon template (coding)DNA strand 5 3’Non template (coding)DNA strand 5 3’UP elementsUP elementsThe C-terminal domain of alpha binds the Upstream Promoter (UP) element (if there is one).The C-terminal domain of alpha binds the Upstream Promoter (UP) element (if there is one).Sigma recyclesSigma recycles closed promoter complex closed promoter complex opened promoter complex opened promoter complex ‘transcription bubble’‘transcription bubble’RNA Pol acts as a helicaseRNA Pol acts as a helicaseRNA Pol acts as a primaseRNA Pol acts as a primaseRNA-DNA hybrid region is 8 bps.The transcription bubbleThe transcription bubbleElongation Elongation (pppG or pppA)(pppG or pppA)gyrasesgyrasesTopoisomerasesTopoisomerasesStrand Elongation ReactionStrand Elongation ReactionOHOHOHOHP-P-PP-P-PFirst nucleotide – ppp A or pppGFirst nucleotide – ppp A or pppGPhosphodiester linkagePhosphodiester linkageTranscription TerminationTranscription Termination-Intrinsic: palindrome sequence + poly-U on nascent RNA-Extrinsic: Rho(ρ)-dependent termination -Intrinsic: palindrome sequence + poly-U on nascent RNA-Extrinsic: Rho(ρ)-dependent terminationIntrinsic Termination SignalIntrinsic Termination SignalAntisense(Template)Intrinsic termination signal Palindrome at the end of a mRNA transcript + poly-U Intrinsic termination signal Palindrome at the end of a mRNA transcript + poly-U RNA hairpinRNA hairpinSeveral uracyl residuesSeveral uracyl residuesIntrinsic TerminationIntrinsic TerminationRho binds rut sites(Rho utilization site)Rho binds rut sites(Rho utilization site)Protein factor Rho(ρ)-dependent terminationProtein factor Rho(ρ)-dependent terminationControl of Bacterial Gene Expression – lac operonControl of Bacterial Gene Expression – lac operon-Galactosidase Induction-Galactosidase InductionOperons allow parallel regulation of functionally related genesOperons allow parallel regulation of functionally related genesgalactosidasegalactosidasepermeasepermeasetransacetylasetransacetylaseRegulation of the Lac Operon transcriptionGlucose, No lactoseRegulation of the Lac Operon transcriptionGlucose, No lactoseXopPolygenic/polycistronic transcriptPolygenic/polycistronic transcriptInducer reduces the affinity of the repressor for the operator DNAInducer reduces the affinity of the repressor for the operator DNAInducers of lac operonInducers of lac operonRegulation of the Lac Operon transcriptionGlucose and LactoseRegulation of the Lac Operon transcriptionGlucose and LactoseRepressorInducerXPositive Regulation of lac Operon by the Catabolite Activator protein (CAP)Positive Regulation of lac Operon by the Catabolite Activator protein (CAP)Glucose = catabolic repressoracts by [cAMP]Glucose = catabolic repressoracts by [cAMP]-61-61Activators can facilitate transcription initiation Activators can facilitate transcription initiation Regulation of the Lac Operon transcriptionLactose, No glucoseRegulation of the Lac Operon transcriptionLactose, No glucoseBiochemistry: The Molecular Basis of Life, 5/e FIGURE 18.41 Roger Kornberg (right) won the 2006 Nobel Prize in Chemistry for his elucidation of the molecular mechanism of eukaryotic transcription. His father, Arthur Kornberg, who died in 2007, received the 1959 Nobel Prize in Physiology or Medicine for his work on prokaryotic DNA polymerases. The Kornberg The KornbergRogerArthurGene Expression in EukaryotesGene Expression in EukaryotesEukaryotes have tissue-specific expressionEukaryotes have tissue-specific expressionEukaryotes have 3 RNA
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