Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 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 37Fig. 10-1Chapter 10: transcriptional regulationRegulation of Gene Transcription DNA-binding proteins• RNA polymerase binding to the transcription initiation site (e.g., promoter) • Regulatory protein(s) binding to other sites (e.g. , operator)• Regulatory protein binding can positively or negatively regulate transcriptionFig. 10-2Positive/negative regulation:binding of activator or repressor proteinsRegulation of Gene Transcription DNA-binding proteins• RNA polymerase binding to the transcription initiation site (e.g., promoter) • Regulatory protein(s) binding to other sites (e.g., operator)• Regulatory protein binding can positively or negatively regulate transcription• Protein affinity for DNA or for other proteins can be influenced by allosteric conformationFig. 10-3Effector binding mediates allosteric changeEffector promotes activator bindingEffector prevents repressor bindingFig. 10-5In mammalian newborns, lactose is the principal sugar source for intestinal floraLactose utilization by E. coli• -linked disaccharide peculiar to milk• lac genes encode a glycosidase and proteins that promote cellular import of lactose• Genes are transcribed only in the presence of lactose (inducible) and the absence of glucose (catabolite repression)• Genes are organized into a co-transcribed cluster (operon; encodes a polycistronic mRNA)Fig. 10-4 lac operon in E. coli(simplified schematic)Fig. 10-6lac operon in E. coli(dynamic schematic)Fig. 10-8Fig. 10-9Fig. 10-10Fig. 10-11Effects of mutations withinconsensus sequences of E. coli promotersFig. 10-12Effects of lac operator mutationsE. coli lac is also regulated by catabolite repression• Regulates preferential utilization of glucose• Mediated by cAMP (glucose-responsive)• cAMP is effector of catabolite activator protein (CAP)• cAMP-CAP binds to lac promoter, enhancing binding of RNA polymeraseFig. 10-13Fig. 10-13Fig. 10-15Activated CAP bindinginduces a distortionof its DNA binding site“presents” P regionto RNA polymeraseFig. 10-16Molecular organization of the lac promoter regionFig. 10-17Cumulative regulatorycontrol of lac transcriptionFig. 10-17Cumulative regulatorycontrol of lac transcriptionFig. 10-18“Negative control”(repression)“Positive control”(activation)Fig. 10-22Typical 5’ end sequences found in eukaryote genes(promoter and nearby elements)RNA polymerasebinding siteFig. 10-23β-globin promoter region and effects of mutationConsensus sequences predict important regionswhich experiments can often confirmFig. 10-24Eukaryote polymerase binding and transcription initiationare determined by cooperative interactions ofdiverse proteins with diverse DNA sequences Near DNA sequences: promoter-proximal elementsDistance-independent DNA sequences: enhancers/silencersEnhancer-binding factors can be tissue-specificFig. 10-27Drosophila dpp gene region contains many tissue-specific enhancersLateral mesoderm enhancer (LE) Imaginal disk enhancer (ID)Visceral mesoderm enhancer (VM)Most tissue/cell-specific gene expression in eukaryotesis controlled by enhancersFig. 10-28Chromosome rearrangements thatcreate new physical relationshipsamong genes can result in gain-of-function mutationThe In(3R)Tab mutationbrings into close proximity:• sr enhancer sequences (drive thorax expression)• Abd-B gene (product drives expression of abdominal pigmentation)+/+ Tab/+Chromatin structure influences gene expressionEuchromatin: rich in active genesHeterochromatin: Constitutive heterochromatin (e.g., centromere regions) few active genesFacultative heterochromatin: euchromatin in some cells,heterochromatic in othersrich in genes; genes are transcriptionally silentEpigenetic inheritance: inheritance of genes with same DNA sequence, but different levels of expressionFig. 10-30Mammalian X-chromosome heterochromatization• dosage compensation• inactivation of one X in female cells (heterochromatic X is “Barr body”)• selection of X occurs in early embryo (then is fixed for clonal populations)• mammalian females mosaically express their X-linked genesImprinting: recently discovered in mammalsDNA methylation usuallyresults in reduced levelsof gene expressionDifferential methylationof genes and transmissionof that methylation canresult in imprintingphenomenaFig. 10-32Fig. 10-31Prader-Willi syndrome can arise “de novo”through a combination of mutation and imprintingFig. 10-34Position-effect variegation (PEV): relocation of euchromatic genesto the vicinity of heterochromatin can result in mosaic inactivationClonal-determined heterochromatin spreadingFig. 10-Fig.