REG1

Summary

Gene Symbol: REG1
Description: protein phosphatase regulator REG1
Alias: HEX2, PZF240, SPP43, SRN1, protein phosphatase regulator REG1
Species: Saccharomyces cerevisiae S288c

Top Publications

  1. Mayordomo I, Regelmann J, Horak J, Sanz P. Saccharomyces cerevisiae 14-3-3 proteins Bmh1 and Bmh2 participate in the process of catabolite inactivation of maltose permease. FEBS Lett. 2003;544:160-4 pubmed
    In this study we show that Reg1, the regulatory subunit of the Reg1/Glc7 protein phosphatase (PP1) complex, interacts physically with the two yeast members of the 14-3-3 protein family, Bmh1 and Bmh2...
  2. Dombek K, Kacherovsky N, Young E. The Reg1-interacting proteins, Bmh1, Bmh2, Ssb1, and Ssb2, have roles in maintaining glucose repression in Saccharomyces cerevisiae. J Biol Chem. 2004;279:39165-74 pubmed
    In Saccharomyces cerevisiae, a type 1 protein phosphatase complex composed of the Glc7 catalytic subunit and the Reg1 regulatory subunit represses expression of many glucose-regulated genes...
  3. Jiang H, Tatchell K, Liu S, Michels C. Protein phosphatase type-1 regulatory subunits Reg1p and Reg2p act as signal transducers in the glucose-induced inactivation of maltose permease in Saccharomyces cerevisiae. Mol Gen Genet. 2000;263:411-22 pubmed
    The REG1 gene encodes a regulatory subunit of the type-1 protein phosphatase (PP1) G1c7 in Saccharomyces cerevisiae, which directs the catalytic subunit to substrates involved in glucose repression...
  4. Becuwe M, Vieira N, Lara D, Gomes Rezende J, Soares Cunha C, Casal M, et al. A molecular switch on an arrestin-like protein relays glucose signaling to transporter endocytosis. J Cell Biol. 2012;196:247-59 pubmed publisher
    ..a direct target of the glucose signaling pathway composed of the AMPK homologue Snf1 and the PP1 phosphatase Glc7/Reg1. Glucose promoted Rod1 dephosphorylation and its subsequent release from a phospho-dependent interaction with 14-3-..
  5. O Donnell A, McCartney R, Chandrashekarappa D, Zhang B, Thorner J, Schmidt M. 2-Deoxyglucose impairs Saccharomyces cerevisiae growth by stimulating Snf1-regulated and α-arrestin-mediated trafficking of hexose transporters 1 and 3. Mol Cell Biol. 2015;35:939-55 pubmed publisher
  6. Vega M, Riera A, Fernández Cid A, Herrero P, Moreno F. Hexokinase 2 Is an Intracellular Glucose Sensor of Yeast Cells That Maintains the Structure and Activity of Mig1 Protein Repressor Complex. J Biol Chem. 2016;291:7267-85 pubmed publisher
    ..of structurally unrelated factors, mainly the DNA-binding Mig1 and Mig2 repressors and the regulatory Snf1 and Reg1 factors. Hxk2 sustains the repressor complex architecture maintaining transcriptional repression at theSUC2gene...
  7. Ludin K, Jiang R, Carlson M. Glucose-regulated interaction of a regulatory subunit of protein phosphatase 1 with the Snf1 protein kinase in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A. 1998;95:6245-50 pubmed
    ..Glucose inhibition of the Snf1-Snf4 interaction depends on protein phosphatase 1 and its targeting subunit, Reg1. Here we show that Reg1 interacts with the Snf1 catalytic domain in the two-hybrid system...
  8. Tu J, Carlson M. REG1 binds to protein phosphatase type 1 and regulates glucose repression in Saccharomyces cerevisiae. EMBO J. 1995;14:5939-46 pubmed
    ..Here, we present evidence that REG1, a protein required for glucose repression, is one such regulatory subunit...
  9. Huang D, Chun K, Goebl M, Roach P. Genetic interactions between REG1/HEX2 and GLC7, the gene encoding the protein phosphatase type 1 catalytic subunit in Saccharomyces cerevisiae. Genetics. 1996;143:119-27 pubmed
    ..Loss of function of the REG1/HEX2 gene, necessary for glucose repression of several genes, was found to suppress the glycogen-deficient phenotype of ..

More Information

Publications61

  1. von Plehwe U, Berndt U, Conz C, Chiabudini M, Fitzke E, Sickmann A, et al. The Hsp70 homolog Ssb is essential for glucose sensing via the SNF1 kinase network. Genes Dev. 2009;23:2102-15 pubmed publisher
    ..Dephosphorylation requires Reg1, which physically targets Glc7 to SNF1...
  2. Dombek K, Camier S, Young E. ADH2 expression is repressed by REG1 independently of mutations that alter the phosphorylation of the yeast transcription factor ADR1. Mol Cell Biol. 1993;13:4391-9 pubmed
    ..REG1/HEX2/SRN1 was identified as a potential serine 230-independent repressor of ADH2 expression...
  3. Lenssen E, James N, Pedruzzi I, Dubouloz F, Cameroni E, Bisig R, et al. The Ccr4-Not complex independently controls both Msn2-dependent transcriptional activation--via a newly identified Glc7/Bud14 type I protein phosphatase module--and TFIID promoter distribution. Mol Cell Biol. 2005;25:488-98 pubmed
    ..Thus, increased activity of STRE genes in ccr4-not mutants may result from both altered general distribution of TFIID and unscheduled activation of Msn2. ..
  4. Jiao R, Postnikoff S, Harkness T, Arnason T. The SNF1 Kinase Ubiquitin-associated Domain Restrains Its Activation, Activity, and the Yeast Life Span. J Biol Chem. 2015;290:15393-404 pubmed publisher
    ..Significantly, the enhanced UBA-dependent longevity and oxidative stress response are at least partially dependent on the Fkh1 and Fkh2 stress response transcription factors, which in turn are shown to influence Snf1 gene expression. ..
  5. Young B, Shin J, Orij R, Chao J, Li S, Guan X, et al. Phosphatidic acid is a pH biosensor that links membrane biogenesis to metabolism. Science. 2010;329:1085-8 pubmed publisher
    ..This enabled coupling of membrane biogenesis to nutrient availability. ..
  6. Maziarz M, Shevade A, Barrett L, Kuchin S. Springing into Action: Reg2 Negatively Regulates Snf1 Protein Kinase and Facilitates Recovery from Prolonged Glucose Starvation in Saccharomyces cerevisiae. Appl Environ Microbiol. 2016;82:3875-3885 pubmed publisher
    ..involves the function of the type 1 protein phosphatase Glc7, which is targeted to Snf1 by a regulatory subunit, Reg1. The reg1 mutation causes increased Snf1 activity and mimics various aspects of glucose limitation, including ..
  7. Ferrer Dalmau J, Randez Gil F, Marquina M, Prieto J, Casamayor A. Protein kinase Snf1 is involved in the proper regulation of the unfolded protein response in Saccharomyces cerevisiae. Biochem J. 2015;468:33-47 pubmed publisher
    ..Analysis of the non-essential mutants in the regulatory subunits of Glc7 revealed that the lack of Reg1, and no other subunit, causes hypersensitivity to unfolded protein response (UPR)-inducers, which was concomitant ..
  8. Tung K, Norbeck L, Nolan S, Atkinson N, Hopper A. SRN1, a yeast gene involved in RNA processing, is identical to HEX2/REG1, a negative regulator in glucose repression. Mol Cell Biol. 1992;12:2673-80 pubmed
    ..Mutations in a single complementation group were obtained. These lesions proved to be in the same gene, SRN1, identified previously in a search for second-site suppressors of mutations that affect the removal of intervening ..
  9. Pasula S, Jouandot D, Kim J. Biochemical evidence for glucose-independent induction of HXT expression in Saccharomyces cerevisiae. FEBS Lett. 2007;581:3230-4 pubmed
    ..Finally, we show that active Snf1 protein kinase in high glucose prevents degradation of Mth1 and Std1. ..
  10. Tabba S, Mangat S, McCartney R, Schmidt M. PP1 phosphatase-binding motif in Reg1 protein of Saccharomyces cerevisiae is required for interaction with both the PP1 phosphatase Glc7 and the Snf1 protein kinase. Cell Signal. 2010;22:1013-21 pubmed publisher
    ..by changes in the rate of dephosphorylation catalyzed by the yeast PP1 phosphatase Glc7 in a complex with the Reg1 protein...
  11. Elbing K, McCartney R, Schmidt M. Purification and characterization of the three Snf1-activating kinases of Saccharomyces cerevisiae. Biochem J. 2006;393:797-805 pubmed
    ..Finally, we showed that the Snf1 kinase domain isolated from bacteria as a GST fusion protein can be activated in vitro and shows substrate specificity in the absence of its beta and gamma subunits. ..
  12. Serra Cardona A, Petrezsélyová S, Canadell D, Ramos J, Ariño J. Coregulated expression of the Na+/phosphate Pho89 transporter and Ena1 Na+-ATPase allows their functional coupling under high-pH stress. Mol Cell Biol. 2014;34:4420-35 pubmed publisher
    ..Our data highlight a scenario in which the activities of Pho89 and Ena1 are functionally coordinated to sustain growth in an alkaline environment. ..
  13. Cannon J, Tatchell K. Characterization of Saccharomyces cerevisiae genes encoding subunits of cyclic AMP-dependent protein kinase. Mol Cell Biol. 1987;7:2653-63 pubmed
    ..SRA1 encodes the regulatory subunit of the cyclic AMP (cAMP)-dependent protein kinase and therefore is identical to REG1 and BCY1...
  14. Bailleul P, Newnam G, Steenbergen J, Chernoff Y. Genetic study of interactions between the cytoskeletal assembly protein sla1 and prion-forming domain of the release factor Sup35 (eRF3) in Saccharomyces cerevisiae. Genetics. 1999;153:81-94 pubmed
    ..We hypothesize that Sup35N is involved in regulatory interactions with intracellular structural networks, and [PSI] prion may be formed as a by-product of this process. ..
  15. Maddock J, Weidenhammer E, Adams C, Lunz R, Woolford J. Extragenic suppressors of Saccharomyces cerevisiae prp4 mutations identify a negative regulator of PRP genes. Genetics. 1994;136:833-47 pubmed
    ..Ten independent recessive suppressors were obtained that identified four complementation groups, spp41, spp42, spp43 and spp44 (suppressor of prp4, numbers 1-4)...
  16. Erickson J, Johnston M. Genetic and molecular characterization of GAL83: its interaction and similarities with other genes involved in glucose repression in Saccharomyces cerevisiae. Genetics. 1993;135:655-64 pubmed
    ..Two other observations were made that suggests that GAL83 functions interdependently with GAL82 and REG1 (another gene involved in glucose repression) to effect glucose repression: 1) REG1 on a low-copy plasmid cross-..
  17. Cui D, Brown C, Chiang H. The type 1 phosphatase Reg1p-Glc7p is required for the glucose-induced degradation of fructose-1,6-bisphosphatase in the vacuole. J Biol Chem. 2004;279:9713-24 pubmed
    ..Taken together, our results suggest that Reg1p-Glc7p interaction and Glc7p phosphatase activity play a required role in the Vid vesicle to vacuole-trafficking step along the FBPase degradation pathway. ..
  18. Wu X, Tatchell K. Mutations in yeast protein phosphatase type 1 that affect targeting subunit binding. Biochemistry. 2001;40:7410-20 pubmed
    ..Many of the mutants are deficient in binding two V/IXF-containing subunits, Gac1 and Reg1, which regulate glycogen accumulation and glucose repression, respectively, but all retain the ability to associate ..
  19. Tomás Cobos L, Viana R, Sanz P. TOR kinase pathway and 14-3-3 proteins regulate glucose-induced expression of HXT1, a yeast low-affinity glucose transporter. Yeast. 2005;22:471-9 pubmed
    ..We also demonstrate that 14-3-3 proteins, in complex with Reg1, a regulatory subunit of Glc7 protein phosphatase, interact physically with Grr1 (a component of the SCF-Grr1 ..
  20. Barrett L, Orlova M, Maziarz M, Kuchin S. Protein kinase A contributes to the negative control of Snf1 protein kinase in Saccharomyces cerevisiae. Eukaryot Cell. 2012;11:119-28 pubmed publisher
    ..Under favorable conditions, Snf1 is turned off by Reg1-Glc7 protein phosphatase. The reg1 mutation causes increased Snf1 activation and slow growth...
  21. Clement S, Dixit G, Dohlman H. Regulation of yeast G protein signaling by the kinases that activate the AMPK homolog Snf1. Sci Signal. 2013;6:ra78 pubmed publisher
    ..b>Reg1, the regulatory subunit of the phosphatase PP1 that acts on Snf1, was likewise required to reverse the ..
  22. Frederick D, Tatchell K. The REG2 gene of Saccharomyces cerevisiae encodes a type 1 protein phosphatase-binding protein that functions with Reg1p and the Snf1 protein kinase to regulate growth. Mol Cell Biol. 1996;16:2922-31 pubmed
    ..Mutants with a deletion of reg1 display a mild slow-growth defect, while reg2 mutants exhibit a wild-type phenotype...
  23. Braun K, Parua P, Dombek K, Miner G, Young E. 14-3-3 (Bmh) proteins regulate combinatorial transcription following RNA polymerase II recruitment by binding at Adr1-dependent promoters in Saccharomyces cerevisiae. Mol Cell Biol. 2013;33:712-24 pubmed publisher
    ..Activating Snf1 by deleting Reg1, a Glc7 protein phosphatase regulatory subunit, is lethal in combination with defective Bmh in strain W303, ..
  24. Ruiz A, Xu X, Carlson M. Roles of two protein phosphatases, Reg1-Glc7 and Sit4, and glycogen synthesis in regulation of SNF1 protein kinase. Proc Natl Acad Sci U S A. 2011;108:6349-54 pubmed publisher
    ..To assess the role of glycogen, we examined Snf1 phosphorylation in strains with altered glycogen metabolism. A reg1? mutant, lacking Reg1-Glc7 protein phosphatase 1, exhibits elevated glycogen accumulation and phosphorylation of ..
  25. Nath N, McCartney R, Schmidt M. Yeast Pak1 kinase associates with and activates Snf1. Mol Cell Biol. 2003;23:3909-17 pubmed
    ..However, deletion of the PAK1 gene suppresses many of the phenotypes associated with the deletion of the REG1 gene, providing genetic evidence that Pak1 activates Snf1 in vivo...
  26. Tachibana C, Biddick R, Law G, Young E. A poised initiation complex is activated by SNF1. J Biol Chem. 2007;282:37308-15 pubmed
  27. Shirra M, Arndt K. Evidence for the involvement of the Glc7-Reg1 phosphatase and the Snf1-Snf4 kinase in the regulation of INO1 transcription in Saccharomyces cerevisiae. Genetics. 1999;152:73-87 pubmed
    ..Dominant mutations in SNF4 and recessive mutations in REG1, OPI1, and RTF2 were isolated that specifically suppress the inositol auxotrophy of the TBP mutant strains...
  28. Braun K, Vaga S, Dombek K, Fang F, Palmisano S, Aebersold R, et al. Phosphoproteomic analysis identifies proteins involved in transcription-coupled mRNA decay as targets of Snf1 signaling. Sci Signal. 2014;7:ra64 pubmed publisher
    ..Deletion of SNF1 rescued the synthetic lethality of simultaneous deletion of XRN1 and REG1, which encodes a regulatory subunit of a phosphatase that inhibits Snf1...
  29. Alms G, Sanz P, Carlson M, Haystead T. Reg1p targets protein phosphatase 1 to dephosphorylate hexokinase II in Saccharomyces cerevisiae: characterizing the effects of a phosphatase subunit on the yeast proteome. EMBO J. 1999;18:4157-68 pubmed
    ..order to identify physiological substrates for the Glc7p-Reg1p complex, we examined the effects of deletion of the REG1 gene on the yeast phosphoproteome...
  30. Mizuno T, Masuda Y, Irie K. The Saccharomyces cerevisiae AMPK, Snf1, Negatively Regulates the Hog1 MAPK Pathway in ER Stress Response. PLoS Genet. 2015;11:e1005491 pubmed publisher
    ..Thus, Snf1 plays pleiotropic roles in ER stress response by negatively regulating the Hog1 MAPK pathway and the UPR pathway. ..
  31. Kimura Y, Irie K, Mizuno T. Expression control of the AMPK regulatory subunit and its functional significance in yeast ER stress response. Sci Rep. 2017;7:46713 pubmed publisher
    ..Our results suggest that the functional significance of the ? subunit of Snf1 AMPK in ER stress response is defined by modulation of the expression level through regulation of the promoter activity. ..
  32. Liu Y, Xu X, Carlson M. Interaction of SNF1 protein kinase with its activating kinase Sak1. Eukaryot Cell. 2011;10:313-9 pubmed publisher
    ..These findings indicate that the C terminus of Sak1 confers its function as the primary Snf1-activating kinase and suggest that the physical association of Sak1 with SNF1 facilitates responses to environmental change. ..
  33. Infante J, Law G, Wang I, Chang H, Young E. Activator-independent transcription of Snf1-dependent genes in mutants lacking histone tails. Mol Microbiol. 2011;80:407-22 pubmed publisher
    ..Deleting REG1, and thus activating Snf1 in the H3 tail mutant enhanced transcription in repressing conditions, indicating that ..
  34. Panni S, Montecchi Palazzi L, Kiemer L, Cabibbo A, Paoluzi S, Santonico E, et al. Combining peptide recognition specificity and context information for the prediction of the 14-3-3-mediated interactome in S. cerevisiae and H. sapiens. Proteomics. 2011;11:128-43 pubmed publisher
    ..Our approach provides an orthogonal reliability assessment and maps with high confidence the 14-3-3 peptide target on the partner proteins. ..
  35. Ruiz A, Liu Y, Xu X, Carlson M. Heterotrimer-independent regulation of activation-loop phosphorylation of Snf1 protein kinase involves two protein phosphatases. Proc Natl Acad Sci U S A. 2012;109:8652-7 pubmed publisher
    ..We further show that the Reg1-Glc7 protein phosphatase 1 and Sit4 type 2A-like phosphatase are largely responsible for dephosphorylation of Thr-..
  36. Lee M, Dohlman H. Coactivation of G protein signaling by cell-surface receptors and an intracellular exchange factor. Curr Biol. 2008;18:211-5 pubmed publisher
    ..Our data suggest that intracellular proteins function in cooperation with mating pheromones to amplify G protein signaling, thereby leading to full pathway activation. ..
  37. Sanz P, Alms G, Haystead T, Carlson M. Regulatory interactions between the Reg1-Glc7 protein phosphatase and the Snf1 protein kinase. Mol Cell Biol. 2000;20:1321-8 pubmed
    Protein phosphatase 1, comprising the regulatory subunit Reg1 and the catalytic subunit Glc7, has a role in glucose repression in Saccharomyces cerevisiae...
  38. Young E, Kacherovsky N, Van Riper K. Snf1 protein kinase regulates Adr1 binding to chromatin but not transcription activation. J Biol Chem. 2002;277:38095-103 pubmed
    ..b>Reg1, represses its binding in the presence of glucose...
  39. García Salcedo R, Lubitz T, Beltran G, Elbing K, Tian Y, Frey S, et al. Glucose de-repression by yeast AMP-activated protein kinase SNF1 is controlled via at least two independent steps. FEBS J. 2014;281:1901-17 pubmed publisher
    ..Co-overexpression of the regulatory subunit Reg1 of the Glc-Reg1 phosphatase complex partly restores glucose regulation of Snf1...
  40. Zhang Y, McCartney R, Chandrashekarappa D, Mangat S, Schmidt M. Reg1 protein regulates phosphorylation of all three Snf1 isoforms but preferentially associates with the Gal83 isoform. Eukaryot Cell. 2011;10:1628-36 pubmed publisher
    ..by changes in the rate of its dephosphorylation, catalyzed by the yeast PP1 phosphatase Glc7 in complex with the Reg1 protein...
  41. Ouyang Q, Ruiz Noriega M, Henry S. The REG1 gene product is required for repression of INO1 and other inositol-sensitive upstream activating sequence-containing genes of yeast. Genetics. 1999;152:89-100 pubmed
    ..Of 31 recessive suppressors of ino4-8 isolated, 29 proved to be alleles of a single locus, identified as REG1, which encodes a regulatory subunit of a protein phosphatase involved in the glucose response pathway...
  42. Hsu H, Liu T, Yeh C, Chang T, Lo Y, Kao C. Feedback Control of Snf1 Protein and Its Phosphorylation Is Necessary for Adaptation to Environmental Stress. J Biol Chem. 2015;290:16786-96 pubmed publisher
    ..Furthermore, artificial elevation of Snf1 phosphorylation (accomplished through deletion of REG1, which encodes a protein that regulates Snf1 dephosphorylation) restored Snf1 protein levels and the regulation of ..
  43. Hess D, Winston F. Evidence that Spt10 and Spt21 of Saccharomyces cerevisiae play distinct roles in vivo and functionally interact with MCB-binding factor, SCB-binding factor and Snf1. Genetics. 2005;170:87-94 pubmed
    ..Analysis of one spt21Delta suppressor, reg1, led to the finding that hyperactivation of Snf1 kinase, as caused by reg1Delta, suppresses the Spt(-) phenotype of ..
  44. Liu Y, Xu X, Singh Rodriguez S, Zhao Y, Kuo M. Histone H3 Ser10 phosphorylation-independent function of Snf1 and Reg1 proteins rescues a gcn5- mutant in HIS3 expression. Mol Cell Biol. 2005;25:10566-79 pubmed
    ..One bypass of Gcn5 requirement gene (BGR) suppressor was mapped to the REG1 locus that encodes a semidominant mutant truncated after amino acid 740...
  45. Parua P, Young E. Binding and transcriptional regulation by 14-3-3 (Bmh) proteins requires residues outside of the canonical motif. Eukaryot Cell. 2014;13:21-30 pubmed publisher
    ..Bmh binding to the Adr1 regulatory domain, and its failure to bind when mutations are present, explains at a molecular level the transcriptional phenotype of ADR1(c) mutants. ..
  46. Bhat W, Boutin G, Rufiange A, Nourani A. Casein kinase 2 associates with the yeast chromatin reassembly factor Spt2/Sin1 to regulate its function in the repression of spurious transcription. Mol Cell Biol. 2013;33:4198-211 pubmed publisher
    ..Taken together, our data suggest that CK2 regulates the function of Spt2 by modulating its interaction with chromatin and the histone chaperone Spt6. ..
  47. Good P, Kendall A, Ignatz Hoover J, Miller E, Pai D, Rivera S, et al. Silencing near tRNA genes is nucleosome-mediated and distinct from boundary element function. Gene. 2013;526:7-15 pubmed publisher
    ..Models for communication between the tRNA gene transcription complexes and local chromatin are discussed. ..
  48. Vyas V, Kuchin S, Berkey C, Carlson M. Snf1 kinases with different beta-subunit isoforms play distinct roles in regulating haploid invasive growth. Mol Cell Biol. 2003;23:1341-8 pubmed
    ..In contrast, the mechanism(s) by which Snf1-Gal83 and Snf1-Sip2 affect filamentation is independent of FLO11. Thus, the Snf1 kinase regulates invasive growth by at least two distinct mechanisms. ..
  49. Gadura N, Robinson L, Michels C. Glc7-Reg1 phosphatase signals to Yck1,2 casein kinase 1 to regulate transport activity and glucose-induced inactivation of Saccharomyces maltose permease. Genetics. 2006;172:1427-39 pubmed
    ..Moreover, we provide evidence that Glc7-Reg1 phosphatase acts as an upstream activator of Yck1,2 kinases in a novel signaling pathway that modulates kinase ..
  50. Dombek K, Voronkova V, Raney A, Young E. Functional analysis of the yeast Glc7-binding protein Reg1 identifies a protein phosphatase type 1-binding motif as essential for repression of ADH2 expression. Mol Cell Biol. 1999;19:6029-40 pubmed
    In Saccharomyces cerevisiae, the protein phosphatase type 1 (PP1)-binding protein Reg1 is required to maintain complete repression of ADH2 expression during growth on glucose...
  51. Entian K, Zimmermann F. New genes involved in carbon catabolite repression and derepression in the yeast Saccharomyces cerevisiae. J Bacteriol. 1982;151:1123-8 pubmed
    A mutation causing resistance to carbon catabolite repression in gene HEX2, mutant allele hex2-3, causes an extreme sensitivity to maltose when in combination with the genes necessary for maltose metabolism...
  52. Matsumoto K, Yoshimatsu T, Oshima Y. Recessive mutations conferring resistance to carbon catabolite repression of galactokinase synthesis in Saccharomyces cerevisiae. J Bacteriol. 1983;153:1405-14 pubmed
    ..These mutations were grouped into three different complementation classes. One class, reg1, contains mutants arising from mutations at a site close to, but complementing, the gal3 locus...