BIOL-L211 Lecture 23 Outline of Last Lecture I. End of PolyadenylationII. Transcriptional TerminationIII. Transcriptional Regulation in EukaryotesIV. Domain Swap ExperimentOutline of Current Lecture I. Activating Domains and DNA-binding DomainsII. Modification of N-terminal Histone TailsIII. ArticleCurrent LectureTranscriptional Regulation in EukaryotesI. Activating Domains and DNA-binding DomainsA. Activating Domains1. Have a structure that is not well defined2. Thus are classified by Amino Acid content instead of structurea. Examples: Acidic, Basic, Hydrophobic, HydrophilicB. DNA-binding Domains1. Well-defined2. Has at least one alpha helix in the major groove of DNA3. That alpha helix is called the recognition helix4. Examples: Homeodomain, Zinc finger, Leucine zipper, Helix-loop-helixThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.5. Homeodomain:a. Series of 3 alpha helicesb. Two helices make a helix-turn-helix motifc. Recognition (3) inserts into major groove (amino acid residues interact with the DNA- specifically Serine, Arginine, and Asparagined. There is additional interaction with the minor groove6. Zinc finger:a. Recognizes the alpha helix and beta pleated sheetb. Cysteine and Histidine residues position zinc ioni. Stabilizes domain foldingii. DNA bindingc. Multiple zinc fingers can occur in a rowC. Activators Again1. Eukaryotic activators are indirect (and interact with RNAP via mediators and TFIID)2. Mediator (recruited by activator) brings Pol II to the promoter region3. General transcription factors are also recruited with mediator, TFIID, or Pol IIa. But may also bind spontaneously4. Nucleosome Modifiers: Help increase expression of genes (recruited by activators)a. Add or remove functional groups to histone tailsb. Remodel the nucleosomeII. Modification of N-terminal Histone Tails (Lecture 7; 9/10/14)A. Modifications are reversible and do not alter the DNA sequenceB. The modifications may change the charge of the core proteinsC. The histone fold domain can also be modifiedD. Histone Acetyltransferases (HATs): Add acetyl groups to histones1. Overall charge becomes more negative2. Chromatin loosensE. Histone Deacetylases (HDACs): Remove acetyl groups1. Chromatin condensesF. Compaction affects ability of transcription factors to access DNAG. Modification of histones process:1. Promoter is wrapped within the nucleosome (and cannot be transcribed)2. Activator binds enhancer and recruits HAT3. HAT acetylates histone tails, loosening chromatin and increasing transcriptionH. Remodeling of Nucleosomes1. Promoter is wrapped within the nucleosome (and cannot be transcribed)2. Activator binds enhancer and recruits chromatin remodeling complex3. Histone charges are not altered, but the DNA bond to the histone core changes4. Transcription then can occurIII. ArticleA. "Regulating Evolution: How Gene Switches Make Life" –Scientific American, May 2008B. Organismal Diversity1. Dissimilar genes and transcriptional regulation account for diversity2. Mutations to enhancers have shaped evolutionC. Regulatory Sequences1. Transcriptional regulators bind to regulatory binding sites on DNA2. Enhancers are a type of regulatory sequencea. Bonding of a transcription factor or activator may increase transcription3. Gene may have multiple enhancersa. In particular when expressed in multiple tissuesb. Changing enhancers may affect where and how a gene is activeD. The Yellow Gene in Fruit Flies: produces black pigment in body and wings1. Multiple enhancers control the expression of this gene2. Enhancer alteration causes alteration in pigment patterns3. Ancestral Fruit Fly (no pigment)a. Low Expression in Wingsb. High Expression in Abdomen4. Fruit Fly with New Featurea. High Expression in Wings due to new enhancerb. High Expression in Abdomen5. Fruit Fly with Loss of Featurea. Low Expression in Wingsb. Low Expression in Abdomen due to loss of
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