1. GAL4 is a specific transcription factor that activates the transcription of several genes inyeast. GAL80 inhibits GAL4's ability to activate (by binding to, and thereby masking, GAL4'sactivation site) unless galactose is available. How might galactose mediate this effect? Onepossibility is that galactose interacts directly with GAL80, changing its conformation and therebychanging the way it interacts with GAL4 (i.e. analogous to the conformational change induced inlac repressor when it binds inducer). However, there is strong evidence arguing against thispossibility. There is genetic evidence that a gene called gal3 (which we will not discuss in class)influences the response of the GAL regulon to galactose. This question concerns the role ofGAL3. The phenotypes associated with mutations in gal3 are shown in the table below. (Notethat gal7 is one of the structural genes regulated by GAL4. Assume that the alleles described inthis table are "null" alleles- that is, they are equivalent to deletion of the corresponding gene.)gal7 transcription-galactosewild-typegal4-gal80-gal3-gal3- gal80-lowlowhighlowhigh+ galactosehighlowhighlowhigh(i) Draw out a regulatory scheme that is consistent with these results and that describesthe regulatory interactions between GAL3, GAL4, and GAL80. Your scheme should bediagrammed using the symbols for activation and repression that we have used previously (e.g.A--> B ---I C--> structural genes.) Your scheme should end with GAL4 --> structural genes.(ii) Now, consider two more pieces of data:(1) A missense mutation in gal80 is discovered that causes GAL80 to inhibit GAL4 even in thepresence of galactose. The gal structural genes are not induced by galactose in this strain. Asecond-site suppressor of this mutation is discovered that maps in gal3; this second mutationrestores the galactose-inducibility of the gal structural genes. (The strain with both mutations isa "pseudo revertant").(2) GAL3 is closely related to the enzyme galactokinase, which uses galactose as a substrate.However, it lacks galactokinase activity. Propose a hypothesis for the molecular roles of GAL80, GAL3, and GAL4 in theregulation of the gal genes. Describe how your hypothesis accounts for each of thefindings outlined above.

Gal3, Gal4 and Gal80 are the protein of saccharomyces cervisae that comprises signal transducer.This…

1. GAL4 is a specific transcription factor that activates the transcription of several genes in yeast. GAL80 inhibits GAL4's ability to activate (by binding to, and thereby masking, GAL4's activation site) unless galactose is available. How might galactose mediate this effect? One possibility is that galactose interacts directly with GAL80, changing its conformation and thereby changing the way it interacts with GAL4 (i.e. analogous to the conformational change induced in lac repressor when it binds inducer). However, there is strong evidence arguing against this possibility. There is genetic evidence that a gene called gal3 (which we will not discuss in class) influences the response of the GAL regulon to galactose. This question concerns the role of GAL3. The phenotypes associated with mutations in gal3 are shown in the table below. (Note that gal7 is one of the structural genes regulated by GAL4. Assume that the alleles described in this table are "null" alleles- that is, they are equivalent to deletion of the corresponding gene.)

1. GAL4 is a specific transcription factor that activates the transcription of several genes in yeast. GAL80 inhibits GAL4's ability to activate (by binding to, and thereby masking, GAL4's activation site) unless galactose is available. How might galactose mediate this effect? One possibility is that galactose interacts directly with GAL80, changing its conformation and thereby changing the way it interacts with GAL4 (i.e. analogous to the conformational change induced in lac repressor when it binds inducer). However, there is strong evidence arguing against this possibility. There is genetic evidence that a gene called gal3 (which we will not discuss in class) influences the response of the GAL regulon to galactose. This question concerns the role of GAL3. The phenotypes associated with mutations in gal3 are shown in the table below. (Note that gal7 is one of the structural genes regulated by GAL4. Assume that the alleles described in this table are "null" alleles- that is, they are equivalent to deletion of the corresponding gene.)

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter10: From Proteins To Phenotypes

Section: Chapter Questions

Problem 21QP: Transcriptional regulators are proteins that bind to promoters (the 5-flanking regions of genes) to...

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Searching the yeast Saccharomyces cerevisiae genome, researchers found approximately 4,000 DNA sites with a sequence which could potentially bind the yeast transcription factor GAL4. GAL4 activates the transcription of galactose genes. Yet there are only 10 GAL4-binding sites which control the genes necessary for galactose metabolism. The GAL4 binding sequence is CGGAT#AGAAGC*GCCG, where # is T, C or G, and * is C or T. In one chromatin immunoprecipitation experiment (ChIP), yeast growing on galactose were lysed, and subjected to cross-linking reagents which cross-linked transcription factors and activators to DNA. Next the DNA was sheared into small fragments, and antibodies to GAL4 were added. These antibodies coprecipitated the GAL4 and the DNA it was cross-linked to. The cross-linking was then chemically reversed, and the DNA was isolated, cloned into a library of plasmids and sequenced. Results showed that only 10 different DNA sequences had GAL4 bound. Since the…
Explain how the following mutations would affect transcription of the yeast GAL1 gene in the presence of galactose. (a) A deletion within the GAL4 gene that removes the region encoding amino acids 1 to 100. (b) A deletion of the entire GAL3 gene. (c) A mutation within the GAL80 gene that blocks the ability of Gal80 protein to interact with Gal3p. (d) A deletion of one of the four UASG elements upstream from the GAL1 gene. (e) A point mutation in the GAL1 core promoter that alters the sequence of the TATA box.
1. Certain proteins that stimulate expression of a gene bind to DNA in a sequence specific manner and also induce conformational changes in the DNA. Describe the purpose of thses two modes of interaction with the DNA. 2. Draw the structures of the amino acid side chains that correspond to the following histone modification: a) acetylation of lysine; b) phosphorylation of serine; c) phosphorylation of histidine. How do thses modifications change the character of their respective side chain?
Suppose that in the formation of phenylalanine hydroxylase mRNA, the exons of the pre-mRNA fail to splice together properly and the resulting enzyme is nonfunctional. This produces an accumulation of high levels of phenylalanine and other compounds, which causes neurological damage. What phenotype would be produced in the affected individual?
Transcriptional regulators are proteins that bind to promoters (the 5-flanking regions of genes) to regulate their transcription. Assume that a particular transcription regulator normally promotes transcription of gene X, a transport protein. If a mutation makes this regulator gene nonfunctional, would the resulting phenotype be similar to a mutation in gene X itself? Why or why not?
6) The C-terminal domain (CTD) of yeast RNA polymerase II (RPB) subunit RPB1 contains the repeating amino acid sequence "-PTSPSYS-". Explain how this sequence plays a role in the regulation of the transcriptional activity of the yeast RPB holoenzyme.
. An interesting mutation in lacI results in repressorswith 110-fold increased binding to both operator andnonoperator DNA. These repressors display a “reverse”induction curve, allowing β-galactosidase synthesis inthe absence of an inducer (IPTG) but partly repressingβ-galactosidase expression in the presence of IPTG. Howcan you explain this? (Note that, when IPTG binds a repressor, it does not completely destroy operator affinity,but rather it reduces affinity 110-fold. Additionally, ascells divide and new operators are generated by thesynthesis of daughter strands, the repressor must findthe new operators by searching along the DNA, rapidlybinding to nonoperator sequences and dissociating fromthem.)
How many ATP and GTP molecules would be hydrolyzed in the synthesis of a 125 amino acid protein? Explain why this is a good argument for careful regulation of gene expression (especially considering that most proteins are larger than 125 amino acids).
Now read this abstract from a 2013 journal article What is the authors' explanation of how Gal80p works? Note UASG from the question above is the same as UASGAL The DNA-binding transcriptional activator Gal4 and its regulators Gal80 and Gal3 constitute a galactose-responsive switch for the GAL genes of Saccharomyces cerevisiae. Gal4 binds to GAL gene UASGAL. (upstream activation sequence in GAL gene pro- moter) sites as a dimer via its N-terminal domain and activates transcription via a C-terminal transcription activation domain (AD). In the absence of galactose, a Gal80 dimer binds to a dimer of Gal4, masking the Gal4AD. Galactose triggers Gal3-Gal80 interaction to rapidly initiate Gal4-mediated transcription activation. Just how Gal3 alters Gal80 to relieve Gals0 inhibition of Gal4 has been unknown, but previous analyses of Gal80 mutants suggested a possible competition between Gal3-Gal80 and Gal80 self-association interactions. Here we assayed Gal80-Gal80 interactions and tested for…
Expression of yeast GAL genes are regulated by Mig1. A Mig1 mutant was identified that could not be phosphorylated. The mutation did not affect any other function of the protein. What effect the mutation will have on GAL expression under the following conditions? In the absence of both galactose and glucose In the presence of galactose and absence of glucose In the presence of both galactose and glucose If you could provide reasoning for your answers that would be great!
The lac genotypes are as shown below: P+OcZ-Y+A+// P¯O+Z+Y+A+ (i) The lac operon consists of three structural genes, lacZ, lacY and lacA. Which structural genes are involved in lactose metabolism? Explain. (ii) Draw and explain how lactose repress the gene expression in lac IS/I- heterozygote. (iii) What is the function of the promoter in the bacterial operon?
1. (a) By binding one L-tryptophan molecule/monomer, the trp repressor binds to DNA to sup- press synthesis of L-tryptophan in E. coli. Below is the amino acid sequence of the helix - reverse turn - helix region of the trp repressor that binds to DNA compared to the sequence of the corresponding DNA binding motif of the Prl protein. A diagram of the trp repressor dimer is also shown. Trp Prl Trp Prl 80 -Gly-Glu-Met-Ser-Gln-Arg-Glu-Leu-Lys-Asn-Glu-Leu-Gly-Ala-Gly-Ile- -Ser-Glu-Glu-Ala-Lys-Glu-Glu-Leu-Ala-Lys-Lys-Cys-Gly-Ile-Thr-Val- trp helix 5 70 trp helix 4 Prl helix 80 Prl helix Ala-Thr-Ile-Thr-Arg-Gly-Ser-Asn-Ser-Leu-Lys-Ala-Ala- Ser-Gln-Val-Ser-Asn-Trp-Phe-Gly-Asn-Lys-Arg-Ile-Arg- reverse turn 90 Comparing the two protein sequences above, identify all amino acid pairs that differ in electrostatic charge due to proton dissociable groups (assume pH 7). Indicate the charge of both residues for each such pair. (b) Circle the pair of residues for which the electrostatic charge due to…