Concept explainers
Although it is customary to consider transcriptional regulation in eukaryotes as resulting from the positive or negative influence of different factors binding to DNA, a more complex picture is emerging. For instance, researchers have described the action of a transcriptional repressor (Net) that is regulated by nuclear export (Ducret et al., 1999. Mol. and Cell. Biol. 19: 7076–7087). Under neutral conditions, Net inhibits transcription of target genes; however, when phosphorylated, Net stimulates transcription of target genes. When stress conditions exist in a cell (for example, from ultraviolet light or heat shock), Net is excluded from the nucleus, and target genes are transcribed. Devise a model (using diagrams) that provides a consistent explanation of these three conditions.
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Essentials of Genetics (9th Edition) - Standalone book
- Discuss the following argument: “if the expression of every gene depends on a set of transcription regulators, then the expression of these regulators must also depend on the expression of other regulators, and their expression must depend on the expression of still other regulators, and so on. cells would therefore need an infinite number of genes, most of which would code for transcription regulators.” how does the cell get by without having to achieve the impossible?arrow_forwardGlenn Croston and his colleagues studied the relation between chromatin structure and transcription activity. In one set of experiments, they measured the level of in vitro transcription of a Drosophila gene by RNA polymerase II in the presence of DNA and various combinations of histone proteins (G. E. Croston et al. 1991. Science 251:643–649). First, they measured the level of transcription of naked DNA, with no associated histone proteins. Then they measured the level of transcription after nucleosome octamers (without H1) were added to the DNA. The addition of the octamers caused the level of transcription to drop by 50%. When both nucleosome octamers and H1 proteins were added to the DNA, transcription was greatly repressed, dropping to less than 1% of that obtained with naked DNA, as shown in the table below. GAL4-VP16 is a protein that binds to the DNA of certain eukaryotic genes. When GAL4-VP16 is added to DNA, the level of transcription by RNA polymerase II is greatly elevated.…arrow_forwardATM is a kinase that phosphorylates histone H2AX in response to double-stranded DNA breaks. Which of the following scenarios would most quickly regulate ATM activity in the cell? a) Adding silencing methyl groups to cytosines in the Atm gene b) Modifying the histone code for the Atm gene c) Increasing expression of a miRNA specific for the Atm mRNA d) Activating an E3 ubiquitin ligase specific for the ATM proteinarrow_forward
- The yeast gene SER3, whose product has a role in serine biosynthesis, is repressed during growth in nutrient-rich medium, so little transcription takes place, and little SER3 enzyme is produced, under these conditions. In an investigation of the repression of the SER3 gene, a region of DNA upstream of SER3 was found to be heavily transcribed when SER3 is repressed ). Within this upstream region is a promoter that stimulates the transcription of an RNA molecule called SRG1 RNA (for SER3 regulatory gene 1). This RNA molecule has none of the sequences necessary for translation. Mutations in the promoter for SRG1 result in the disappearance of SRG1 RNA, and these mutations remove the repression of SER3. When RNA polymerase binds to the SRG1 promoter, the polymerase travels downstream, transcribing the SGR1 RNA, and passes through and transcribes the promoter for SER3. This activity leads to the repression of SER3. Propose a possible explanation for how the transcription of SGR1 might…arrow_forwardDebes et al recently described how aging in humans, mice, nematodes, and other eukaryotes is associated with an increase in the average speed of transcriptional elongation by RNA polymerase II. Overexpression of some proteins that decreased PolII elongation speed extended lifespan in the fly Drosophila. For each of the following proteins, predict whether overexpression of that protein (assuming all other cellular components are normal) would likely reduce transcriptional speed, and briefly justify your answer. a) Mediator proteinsb) Histone proteinsc) Insulator binding proteinsarrow_forwardDiscuss how the expression of a protein can be regulated post transcription in eukaryotic cells through, using the following key terms: Degradation of mRNA (two ways) Blocking translation Degradation of the proteinarrow_forward
- Chromatin Immunoprecipitation (ChIP) experiments enable researchers to measure the levels of transcription factors, coactivators/corepressors and chromatin remodeling complexes on a specific gene in cells. In the ChIP experiment below, the recruitment of the transcription factor NfkB, Histone Deacetylase Complex (HDAC3) and p300/CBP complex to the Interleukin 12 (IL12) gene at various times (0, 30, 60 and 120 min) after treating cells with LPS are measured. Does LPS stimulate or inhibit transcription of the IL12 gene based on the recruitment of factors to the IL12 gene. Justify your answer by explaining the state of the gene before LPS and after LPS treatment (limit 5-6 sentences).arrow_forwardRNAP can access the lacz promoter irrespective of whether CAP-CAMP is binding the CAP O True O Falsearrow_forwardWhich of the following is the most likely result of a mutation in the lac operator that prevents release of the depressor protein? Choose 1 answer: (A)The lactose permease protein will be produced, even in the absence of lactose. (B) Transcription of the structural genes will be blocked, even in the presence of lactose. (C) The catabolite activator protein will be bound to the CAP site, even in the presence of glucose. (D) Expression of the lacI gene will be repressed, even in the absence of glucose.arrow_forward
- The yeast gene SER3, whose product has a role in serine biosynthesis, is repressed during growth in nutrient-rich medium, so little transcription takes place, and little SER3 enzyme is produced, under these conditions. In an investigation of the repression of the SER3 gene, a region of DNA upstream of SER3 was found to be heavily transcribed when SER3 is repressed (J. A. Martens, L. Laprade, and F. Winston. 2004. Nature 429:571–574). Within this upstream region is a promoter that stimulates the transcription of an RNA molecule called SRG1 RNA (for SER3 regulatory gene 1). This RNA molecule has none of the sequences necessary for translation. Mutations in the promoter for SRG1 result in the disappearance of SRG1 RNA, and these mutations remove the repression of SER3. When RNA polymerase binds to the SRG1 promoter, the polymerase travels downstream, transcribing the SGR1 RNA, and passes through and transcribes the promoter for SER3. This activity leads to the repression of SER3. Propose…arrow_forwardConsider the Rho-dependent terminator sequence 5’CCCAGCCCGCCUAAUGAGCGGCCUUUUUUUU-3’. What affect would a point mutation at any one of the bolded and underlined nucleotides disrupt termination of transcription? Group of answer choices Mutation in one of these nucleotides would disrupt base pairing, preventing the formation of the hairpin and disrupting termination. Mutation in one of these nucleotides would have no affect on base pairing, so the termination hairpin is formed and termination proceeds. Mutation in one of these nucleotides would not disrupt base pairing, but would prevent the formation of the hairpin and disrupt termination. Mutation in one of these nucleotides would disrupt base pairing, but not affect the formation of the hairpin and termination proceeds.arrow_forwardTranscriptional regulators are proteins that bind to promoters (at the 5’ flanking regions of genes) to regulate their transcription. Assume that a particular transcription regulator normally promotes transcription of gene X that codes for a membrane transport protein. If a mutation makes this transcription regulator nonfunctional, would the resulting phenotype be similar to a deleterious mutation in the membrane transporter itself? Why or why not?arrow_forward
- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage LearningBiology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning