BIOL 3451 1st Edition Lecture 23 Outline of Last Lecture I. 17.2 Programmed DNA Rearrangements Regulate Expression of a Small Number of GenesII. 17.3 Eukaryotic Gene Expression Is Influenced by Chromatin Modifications III. 17.4 Eukaryotic Transcription Initiation Is Regulated at Specific Cis-Acting Sites IV. 17.5 Eukaryotic Transcription Initiation Is Regulated by Transcription Factors That Bind toCis-Acting SitesV. 17.6 Activators and Repressors Interact with General Transcription Factors at the PromoterVI. 17.7 Gene Regulation in a Model Organism: Transcription of the GAL genes of YeastOutline of Current Lecture I. 17.7 Gene Regulation in a Model Organism: Transcription of the GAL genes of Yeast II. 17.8 Posttranscriptional Gene Regulation Occurs at All the Steps from RNA Processing to Protein ModificationIII. 17.9 RNA Silencing Controls Gene Expression in Several WaysIV. 19.1 Cancer is a Genetic Disease That Arises at the Level of Somatic CellsV. 19.2 Cancer Cells Contain Genetic Defects Affecting Genomic Stability, DNA Repair, and Chromatin ModificationsCurrent LectureI. 17.7 Gene Regulation in a Model Organism: Transcription of the GAL genes of Yeasto GAL1 and GAL10 controlled by central control region (UASG)- UAS are functionally similar to enhancers in eukaryotes- Four binding sites for Gal4 protein (regulator)- Fig 17.11- Chromatin structure of UAS is constitutively open, or DNase hypersensitive, meaning that it is free of nucleosomeso Mutation in the regulator of GAL4 prevents activation- Thus, Gal80p is positive regulator (controls transcription this way)1. Regulator must be present to turn on gene transcriptionII. 17.8 Posttranscriptional Gene Regulation Occurs at All the Steps from RNA Processing to Protein Modificationo Transcriptional control major type of regulation in eukaryotes, posttranscriptionalregulation plays just as much of a role, or moreThese 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.- Includes: 1. Removal of introns and splicing together of exons2. Addition of a cap and poly-A tail3. Translation4. Stabilityo Alternative splicing: generate different forms of mRNA from identical pre-mRNA, gives rise to a number of proteins from one gene (splice exon as in intron to change protein functions)- as a result…number of proteins that a cell can make (its proteome) is not directly related to number of genes in genome- our bodies make like a million different proteins, but down to about 25,000 genes (how possible?....alternative splicing- we think about 2/3 of genes do alternative splicing- allows humans to produce several hundred thousand different proteins from like 25,000 genes- mutations (in some diseases) affect regulation of splicing (spliceopathies) 1. fragile X, Huntington, myotonic dystrophy2. fig 17.13a. four is skipped (stop codon there bc became intron), 1-2-3-5-6 b. can get: functionally similar results or something quite differento Sex lethal (Sxl), transformer (tra), doublesex (dsx) genes are part of a hierarchy ofgene regulation for sex determination in D rosophila- Fig 17.15: signaling cascade results in male or femaleo Steady-state level: amount of mRNA in a cell; determined by combination of transcription rate and rate of mRNA degradation- Determines amount of mRNA available for translation and regulated in response to cellular needs- Can be regulated in many ways1. Degradation (done by higher eukaryotes, best way found so far to do this)2. Translational level (blocking using repressors)3. Posttranslational stability of protein can be modulatea. P53 protein b. Can change structure and hence, activityIII. 17.9 RNA Silencing Controls Gene Expression in Several Wayso RNA silencing can be used- Not done a lot in humans, but in plants yes- Short RNA molecules regulate gene expression by triggering mRNA degradation and repressing translation1. Posttranscriptional regulation known as RNA interference (RNAi)2. Together, these phenomena known as RNA-induced gene silencingo RNAi uses protein DICER to cut up double stranded mRNA into small interfering RNAs (siRNAs) and micro RNAs (miRNAs)- Repress MRNA translation and trigger degradation- Bind to mRNA through DICER (when base pairs, means I should kill you)- Inhibit transcription of specific genes by associating with RNA-induced initiation of transcription (RITS) and RNA-induced silencing complex (RISC complex) - Fig. 17.16o RNAi technology: big in lab, and now looking at pharmaceutical agent- Study diseases caused by overexpression of specific gene or normal expression of abnormal gene product (use RNAi to as therapeutic product)- Results in reducing severity of HIV and influenza, polio- Animal models1. Viral infection2. Eye diseases3. Cancer4. Inflammatory bowel disease- RNAi holds powerful promise for molecular medicineIV. 19.1 Cancer is a Genetic Disease That Arises at the Level of Somatic Cellso Genetic disease at the somatic level resulting from mutated gene products or abnormally expressed genes- Can inherit vulnerabilities, but most often, done to ourselves- Two fundamental properties:1. Unregulated cell proliferation2. Metastatic spread (usually what kills you)o Mutations- Single-nucleotide substitutions- Large-scale chromosomal rearrangements- Amplifications (quantity, not quality issue)- Deletions- Usually, there are multiple nucleotide changes- Fig 19.1o Most cancers are somatic, the inherited risk for cancer is large (1% due to germ-line mutations)- Rarely arises from gene mutations, but usually from accumulation of mutations in many genes (6-12)- These affect DNA repair (usually results in different kinds of cancer), cell division (very common), apoptosis, cellular differentiation, migratory behavior and cell-cell contact (metastatic) - Fig 19.1 (lots of aneuploidy)1. Lots of translocation (different colors on chromosomes)- Benign tumors: don’t move and probably won’t kill you unless in a really bad spot; most cases, easily removable by surgery; can be deadly if not removed (depending on area)- Malignant tumors: when begins to spread by metastasis (invading other tissue); becomes life-threateningo All cancer cells in primary and secondary tumors are clonal: means that they originate from one cell that accumulated numerous specific mutations- Reciprocal translocations are characteristic of many cancerso Burkitt’s lymphoma: shows reciprocal translocations between