BCHM 3050 1st Edition Lecture 26 Outline of Last Lecture I. Transcriptional RegulationII. Epigenetic RegulationIII. Regulation of Gene ExpressionOutline of Current LectureI. Blocking of Transcription or Translation by AntibioticsII. Epigenetic Regulation ExamplesIII. Regulation of Gene Expression in EukaryotesIV. Locus Control Region (LCR)V. RNA Processing-Alternative RNA SplicingVI. mRNA DegradationVII. OperonsVIII. DNA Binding ProteinsIX. Glucose vs. LactoseX. PROGXI. Activation of Lac OperonXII. Role of Catabolite Activating ProteinCurrent LectureXIII. Blocking of Transcription or Translation by AntibioticsThese 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.a. Tetracycline – blocks A-site to prevent translationb. Chloramphenicol – inhibits peptidyl transferasec. Erythromycin – blocks translocation d. Alpha – Amanitin – blocks transcription ONLY in eukaryotes, binds to RNA Polymerase IIe. Cordycepin – blocks messenger RNA, works against translation (fungus in caterpillar)XIV. Epigenetic Regulation Examplesa. This occurs on chromosome #19b. IGF2 and H19 are on the same chromosome (inherit one from mom and one from dad)c. One can be turned off and passed onto offspring – Mom’s IGF2 is silenced and Dad’s H19 is silenced across all humansd. Example of epigenetics that is not affected by the environmente. If you do not express H19 à Angelman Syndrome (no H19; mental disabilities and sterility issues)f. If IGF2 is silenced à Prader-Willi Syndrome (no IGF2)g. Women and med produce the same amount of proteins from the X chromosome because 1 of the woman’s X chromosomes is silenced (Barr bodies) à gender based epigeneticsXV. Regulation of Gene Expression in Eukaryotesa. Promoters bind RNA polymerase and sometimes activatorsb. Activation (proteins) à Enhancersc. Activators RNA polymerase (proteins) à promotesd. Modulators – middle man that are sometimes needed, but not always; protein example of positive regulatore. Connect RNA polymerase with activatorf. Enhancers, promoters, silencers are DNAg. Activators, RNA polymerase, repressors are proteins that bind to DNAXVI. Locus Control Region (LCR)a. Beta Thalessemia is as common as cystic fibrosisb. Beta subunit of hemoglobin is disfunctionalc. LCR is an example of an enhancerd. If you have a mutation in the enhancer for the globin gene à diseaseXVII. RNA Processing-Alternative RNA Splicinga. Body makes one huge RNA strand with introns and exons and then the spliceosome enzyme complex regulates which mRNA to create based on the exons included in splicing (alternate splicing)b. Example of Post transcriptional modifications (along with capping and adding a poly A tail)XVIII. mRNA Degradationa. Understand what the miRNA and siRNA doi. siRNA – small interfering RNAii. miRNA - microRNAb. Translational regulation:i. miRNA sticks to target mRNA and either degrades it or blocks translation machinery from attaching to itii. miRNA and siRNA are made in our body and stick to a certain mRNA or can promote loss of translationXIX. Operonsa. Prokaryotes use operons, which have one regulatory unit (one promoter) for multiple genesb. One promoter that affects multiple genes at onceXX. DNA Binding Proteinsa. DNA binding proteins – repressor, activator, histone, etc.b. Most DNA binding proteins have these 4 motifs: helix-turn-helix, zinc fingers, leucine zippers, helix-loop-helixc. If a protein has any of these motifs, it can probably bind to DNAd. DNA binding domain is rich in alpha helicese. DNA binding proteins need weak interactions like hydrogen interactions but NEVER covalent bonds (because the protein eventually needs to let go)f. Generally have glutamic acid residues which interact with basic residuesg. Positive regulation – carried out be activators and allows for transcriptionh. Negative regulation – carried out be repressors and prevent transcription from occurringi. Repression turns off genej. Derepression turns on geneXXI. Glucose vs. Lactosea. Glucose is a six-membered ringb. When glucose and galactose come together à lactosec. Glycosidic bond between the two sugars that for lactosed. Isomer of lactose is allo-lactosee. Lactose is broken down into glucose and galactose, but some of it doesn’t get broken down and turns into allo-lactosef. The ability to break down lactose is an adapted trait, so some people are still lactose-intolerantXXII. PROGa. Promoter – Repressor protein (different from the protein in eukaryotes) – Operator (only in prokaryotes) – Genesb. Repressor is constantly being made in bacteriac. As long as operon is bound to repressor protein, it is turned off and the gene cannot be maded. The operon is constantly off in bacteria, and it gets turned on in special occasionsXXIII. Activation of Lac Operona. When lactose is present in the medium and the bacteria does no have glucose, then the allo-lactose can bind to the repressor and remove it from the operator, so that the operon can turn on b. The enzymes are needed to break down and use lactose:c. Permease helps to get lactose into the celld. Galactosidase helps to break down lactosee. Transacetylase helps to convert lactose to glucose to be used by the cellXXIV. Role of Catabolite Activating Proteina. When there is no glucose , ATP converts to cAMP à cAMP binds to CAP and serves as an activator and makes more genes (increases the rate of transcription by about 50 times and promotes gene transcription)b. Glucose will convert cAMP back to ATP when prevent c. Glucose reverses the balance of how much cAMP present in the
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