Generalities for Generalities for Transcriptional Transcriptional Regulation Regulation • Activators and Repressors Act in Activators and Repressors Act in Concert Concert • Effector Binding Changes Protein Effector Binding Changes Protein Shape Shape • DNA Binding Occurs at Specific DNA Binding Occurs at Specific Sequences Sequences • DNA Looping Common Feature DNA Looping Common Feature
Generalities for Transcriptional Regulation. Activators and Repressors Act in Concert Effector Binding Changes Protein Shape DNA Binding Occurs at Specific Sequences DNA Looping Common Feature. Eukaryotes vs. Prokaryotes. Complexity of Genome Multiple, Compartmentalized Chromosomes - PowerPoint PPT Presentation
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Generalities for Transcriptional Generalities for Transcriptional RegulationRegulation
• Activators and Repressors Act in ConcertActivators and Repressors Act in Concert
• Effector Binding Changes Protein ShapeEffector Binding Changes Protein Shape
• DNA Binding Occurs at Specific SequencesDNA Binding Occurs at Specific Sequences
• DNA Looping Common FeatureDNA Looping Common Feature
Eukaryotes vs. ProkaryotesEukaryotes vs. Prokaryotes
Chromatin Structure and Gene ExpressionChromatin Structure and Gene Expression
• Dampens Transcription to Low LevelsDampens Transcription to Low Levels• Major Means of Keeping Expression Turned Major Means of Keeping Expression Turned
• Reflected by DNAase I hypersensitivityReflected by DNAase I hypersensitivity
• Heterochromatin Silences All TranscriptionHeterochromatin Silences All Transcription– Example: X-inactivation and formation of Barr Example: X-inactivation and formation of Barr
BodiesBodies
Sex Determination in Sex Determination in DrosophilaDrosophila
• XX Females, XY MalesXX Females, XY Males– Early Embryo “Counts” the X ChromosomesEarly Embryo “Counts” the X Chromosomes
• Sex Lethal (Sxl) Gene Critical RegulatorSex Lethal (Sxl) Gene Critical Regulator– Mutations in Sxl Result in NO Females!Mutations in Sxl Result in NO Females!
• Sex Lethal Acts at the Level of SplicingSex Lethal Acts at the Level of Splicing– RNA-Binding Splice Factor RNA-Binding Splice Factor
mRNA lacks premature stop codon;mRNA lacks premature stop codon;transformer protein functionaltransformer protein functional
Males (XY)Males (XY) Females (XX)Females (XX)
after Fig. 16.16
Regulation of Gene Expression via RNA StabilityRegulation of Gene Expression via RNA Stability
RNA RNA in situin situ
Northern BlotNorthern Blot
Mechanisms to Degrade mRNAMechanisms to Degrade mRNA
• Poly-A Tail LengthPoly-A Tail Length– Long tails confer stabilityLong tails confer stability• Tail shortening leads to mRNA turnoverTail shortening leads to mRNA turnover
• Degradation SequencesDegradation Sequences– Map to 3’ (or 5’) Untranslated RegionsMap to 3’ (or 5’) Untranslated Regions• Interact with protein factors that degrade Interact with protein factors that degrade
the “targeted” mRNAthe “targeted” mRNA
Reporter Constructs Are Used Reporter Constructs Are Used to Identify Degradation Sequencesto Identify Degradation Sequences