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Fouet M, Rine J. Limits to transcriptional silencing in Saccharomyces cerevisiae. Genetics 2022; 223:6887216. [PMID: 36495285 PMCID: PMC9910407 DOI: 10.1093/genetics/iyac180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 09/12/2022] [Accepted: 11/11/2022] [Indexed: 12/14/2022] Open
Abstract
Mating-type switching in the budding yeast Saccharomyces cerevisiae relies on the Sir protein complex to silence HML and HMR, the two loci containing copies of the alleles of the mating type locus, MAT. Sir-based transcriptional silencing has been considered locus-specific, but the recent discovery of rare and transient escapes from silencing at HMLα2 with a sensitive assay called to question if these events extend to the whole locus. Adapting the same assay, we measured that transient silencing failures at HML were more frequent for the α2 gene than α1, similarly to their expression level in unsilenced cells. By coupling a mating assay, at HML we found that one of the two genes at that locus can be transiently expressed while the other gene is maintained silent. Thus, transient silencing loss can be a property of the gene rather than the locus. Cells lacking the SIR1 gene experience epigenetic bistability at HML and HMR. Our previous result led us to ask if HML could allow for two independent epigenetic states within the locus in a sir1Δ mutant. A simple construct using a double fluorescent reporter at HMLα1 and HMLα2 ruled out this possibility. Each HML locus displayed a single epigenetic state. We revisited the question of the correlation between the states of two HML loci in diploid cells, and showed they were independent. Finally, we determined the relative strength of gene repression achieved by Sir-based silencing with that achieved by the a1-α2 repressor.
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Affiliation(s)
- Marc Fouet
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Jasper Rine
- Corresponding author: Department of Molecular and Cellular Biology, California Institute of Quantitative Biosciences, 406 Barker Hall, U.C. Berkeley, Berkeley, CA 94720-3202, USA.
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Aranda-Díaz A, Mace K, Zuleta I, Harrigan P, El-Samad H. Robust Synthetic Circuits for Two-Dimensional Control of Gene Expression in Yeast. ACS Synth Biol 2017; 6:545-554. [PMID: 27930885 PMCID: PMC5507677 DOI: 10.1021/acssynbio.6b00251] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Cellular phenotypes are the result of complex interactions between many components. Understanding and predicting the system level properties of the resulting networks requires the development of perturbation tools that can simultaneously and independently modulate multiple cellular variables. Here, we develop synthetic modules that use different arrangements of two transcriptional regulators to achieve either concurrent and independent control of the expression of two genes, or decoupled control of the mean and variance of a single gene. These modules constitute powerful tools to probe the quantitative attributes of network wiring and function.
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Affiliation(s)
- Andrés Aranda-Díaz
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California 94158, United States
- California Institute for Quantitative Biosciences, University of California San Francisco, San Francisco, California 94158, United States
| | - Kieran Mace
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California 94158, United States
- California Institute for Quantitative Biosciences, University of California San Francisco, San Francisco, California 94158, United States
| | - Ignacio Zuleta
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California 94158, United States
- California Institute for Quantitative Biosciences, University of California San Francisco, San Francisco, California 94158, United States
| | - Patrick Harrigan
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California 94158, United States
- California Institute for Quantitative Biosciences, University of California San Francisco, San Francisco, California 94158, United States
| | - Hana El-Samad
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California 94158, United States
- California Institute for Quantitative Biosciences, University of California San Francisco, San Francisco, California 94158, United States
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Niranjan T, Guo X, Victor J, Lu A, Hirsch JP. Kelch repeat protein interacts with the yeast Galpha subunit Gpa2p at a site that couples receptor binding to guanine nucleotide exchange. J Biol Chem 2007; 282:24231-8. [PMID: 17584745 DOI: 10.1074/jbc.m702595200] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The kelch repeat-containing proteins Krh1p and Krh2p are negative regulators of the Gpa2p signaling pathway that directly interact with the G protein alpha-subunit Gpa2p in the yeast Saccharomyces cerevisiae. A screen was carried out to identify Gpa2p variants that are defective in their ability to bind Krh1p but retain the ability to bind another Gpa2p-interacting protein, Ime2p. This screen identified amino acids Gln-419 and Asn-425 as being important for the interaction between Gpa2p and Krh1p. Gpa2p variants with changes at these positions are defective for Krh1p binding in vivo. Cells containing these forms of Gpa2p display decreased heat shock resistance and increased expression of a gene required for pseudohyphal growth. These findings indicate that the substitutions at positions 419 and 425 confer a degree of constitutive activity to the Gpa2p alpha-subunit. Residues Gln-419 and Asn-425 are located in the beta6-alpha5 loop and alpha5 helix of Gpa2p, which is the region that couples receptor binding to guanine nucleotide exchange. The results suggest that binding of Gpa2p to Krh1p does not resemble the binding of Galpha subunits to either Gbeta subunits or effectors, but it instead represents a novel type of functional interaction.
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Affiliation(s)
- Thiruvur Niranjan
- Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, New York 10029, USA
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Abstract
The intracellular signal transduction pathway by which the yeast Saccharomyces cerevisiae responds to the presence of peptide mating pheromone in its surroundings is one of the best understood signaling pathways in eukaryotes, yet continues to generate new surprises and insights. In this review, we take a brief walk down the pathway, focusing on how the signal is transmitted from the cell-surface receptor-coupled G protein, via a MAP kinase cascade, to the nucleus.
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Affiliation(s)
- Lee Bardwell
- Department of Developmental and Cell Biology, 2208 Natural Sciences I, University of California, Irvine, CA 92697-2300, USA.
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Abstract
The intracellular signal transduction pathway by which the yeast Saccharomyces cerevisiae responds to the presence of peptide mating pheromone in its surroundings is one of the best understood signaling pathways in eukaryotes, yet continues to generate new surprises and insights. In this review, we take a brief walk down the pathway, focusing on how the signal is transmitted from the cell-surface receptor-coupled G protein, via a MAP kinase cascade, to the nucleus.
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Affiliation(s)
- Lee Bardwell
- Department of Developmental and Cell Biology, 2208 Natural Sciences I, University of California, Irvine, CA 92697-2300, USA.
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Roth AF, Nelson B, Boone C, Davis NG. Asg7p-Ste3p inhibition of pheromone signaling: regulation of the zygotic transition to vegetative growth. Mol Cell Biol 2000; 20:8815-25. [PMID: 11073982 PMCID: PMC86523 DOI: 10.1128/mcb.20.23.8815-8825.2000] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The inappropriate expression of the a-factor pheromone receptor (Ste3p) in the MATa cell leads to a striking inhibition of the yeast pheromone response, the result of a functional interaction between Ste3p and some MATa-specific protein. The present work identifies this protein as Asg7p. Normally, expression of Ste3p and Asg7p is limited to distinct haploid mating types, Ste3p to MATalpha cells and Asg7p to MATa cells. Artificial coexpression of the two in the same cell, either a or alpha, leads to dramatic inhibition of the pheromone response. Ste3p-Asg7p coexpression also perturbs the membrane trafficking of Ste3p: Ste3p turnover is slowed, a result of an Asg7p-mediated retardation of the secretory delivery of the newly synthesized receptor to the plasma membrane. However, in the absence of ectopic Ste3p expression, the asg7Delta mutation is without consequence either for pheromone signaling or overall mating efficiency of a cells. Indeed, the sole phenotype that can be assigned to MATa asg7Delta cells is observed following zygotic fusion to its alpha mating partner. Though formed at wild-type efficiency, zygotes from these pairings are morphologically abnormal. The pattern of growth is deranged: emergence of the first mitotic bud is delayed, and, in its place, growth is apparently diverted into a novel structure superficially resembling the polarized mating projection characteristic of haploid cells responding to pheromone. Together these results suggest a mechanism in which, following the zygotic fusion event, Ste3p and Asg7p gain access to one another and together act to repress the pheromone response, promoting the transition of the new diploid cell to vegetative growth.
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Affiliation(s)
- A F Roth
- Department of Surgery, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
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Kim J, Bortz E, Zhong H, Leeuw T, Leberer E, Vershon AK, Hirsch JP. Localization and signaling of G(beta) subunit Ste4p are controlled by a-factor receptor and the a-specific protein Asg7p. Mol Cell Biol 2000; 20:8826-35. [PMID: 11073983 PMCID: PMC86527 DOI: 10.1128/mcb.20.23.8826-8835.2000] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Haploid yeast cells initiate pheromone signaling upon the binding of pheromone to its receptor and activation of the coupled G protein. A regulatory process termed receptor inhibition blocks pheromone signaling when the a-factor receptor is inappropriately expressed in MATa cells. Receptor inhibition blocks signaling by inhibiting the activity of the G protein beta subunit, Ste4p. To investigate how Ste4p activity is inhibited, its subcellular location was examined. In wild-type cells, alpha-factor treatment resulted in localization of Ste4p to the plasma membrane of mating projections. In cells expressing the a-factor receptor, alpha-factor treatment resulted in localization of Ste4p away from the plasma membrane to an internal compartment. An altered version of Ste4p that is largely insensitive to receptor inhibition retained its association with the membrane in cells expressing the a-factor receptor. The inhibitory function of the a-factor receptor required ASG7, an a-specific gene of previously unknown function. ASG7 RNA was induced by pheromone, consistent with increased inhibition as the pheromone response progresses. The a-factor receptor inhibited signaling in its liganded state, demonstrating that the receptor can block the signal that it initiates. ASG7 was required for the altered localization of Ste4p that occurs during receptor inhibition, and the subcellular location of Asg7p was consistent with its having a direct effect on Ste4p localization. These results demonstrate that Asg7p mediates a regulatory process that blocks signaling from a G protein beta subunit and causes its relocalization within the cell.
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Affiliation(s)
- J Kim
- Department of Cell Biology and Anatomy, Mount Sinai School of Medicine, New York, New York 10029, USA
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Fowler TJ, DeSimone SM, Mitton MF, Kurjan J, Raper CA. Multiple sex pheromones and receptors of a mushroom-producing fungus elicit mating in yeast. Mol Biol Cell 1999; 10:2559-72. [PMID: 10436012 PMCID: PMC25488 DOI: 10.1091/mbc.10.8.2559] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The mushroom-producing fungus Schizophyllum commune has thousands of mating types defined, in part, by numerous lipopeptide pheromones and their G protein-linked receptors. Compatible combinations of pheromones and receptors encoded by different mating types regulate a pathway of sexual development leading to mushroom formation and meiosis. A complex set of pheromone-receptor interactions maximizes the likelihood of outbreeding; for example, a single pheromone can activate more than one receptor and a single receptor can be activated by more than one pheromone. The current study demonstrates that the sex pheromones and receptors of Schizophyllum, when expressed in Saccharomyces cerevisiae, can substitute for endogenous pheromone and receptor and induce the yeast pheromone response pathway through the yeast G protein. Secretion of active Schizophyllum pheromone requires some, but not all, of the biosynthetic machinery used by the yeast lipopeptide pheromone a-factor. The specificity of interaction among pheromone-receptor pairs in Schizophyllum was reproduced in yeast, thus providing a powerful system for exploring molecular aspects of pheromone-receptor interactions for a class of seven-transmembrane-domain receptors common to a wide range of organisms.
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Affiliation(s)
- T J Fowler
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont 05405, USA
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