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Gene Review

LRG1  -  Lrg1p

Saccharomyces cerevisiae S288c

Synonyms: LIM-RhoGAP protein 1, Rho-GTPase-activating protein LRG1, YDL240W
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High impact information on LRG1

  • We here report the sequence of a yeast gene LRG1 whose deduced amino acid sequence contains sequence motifs similar to LIM domain proteins in the amino-terminal, and to rho/rac GTPase activating proteins (rho/racGAP's) in the carboxy-terminal part [1].
  • Strikingly, however, deletion of LRG1 rescued the growth defects associated with Cdc34/SCF mutants, whereas deletion of SAC7 enhanced these defects [2].
  • BEM1 and FUS1 were high-copy suppressors of many cell-fusion-defective mutations, whereas LRG1 suppressed only fus2Delta and rvs161Delta [3].
  • Higher dosage of three genes, BEM1, LRG1, and FUS1, partially suppressed the fus2Delta cell fusion defect [3].
  • High-copy LRG1 suppressed the mislocalization of beta(1-3) glucan in fus2Delta strains [3].

Biological context of LRG1

  • (1) Deletion of LRG1 suppresses the growth phenotypes associated with mutations in SLG1 (which codes for a putative sensor of cell wall damage) [4].
  • Complete deletion of LRG1, as well as deletion of the Rho-GAP coding region, caused decreased rates of cell fusion and diploid formation comparable to that of fus2Delta [3].
  • LRG1, previously characterized as a Rho-GAP that regulates beta-1,3-glucan synthesis, was identified using a filtration screen designed to isolate genes that promote cell aggregation in Sigma1278b Saccharomyces cerevisiae [5].
  • Additionally, this phenotype required sufficient nitrogen. beta-1,3-Glucan content was elevated in lrg1 haploids and these cells possessed a thicker cell wall and septum than wild-type strains [5].
  • Two-hybrid analyses of Lrg1p, which contains a sequence conserved among Rho GTPase-activating proteins (GAPs), revealed its specific interactions with the active form of Rho1p [6].

Anatomical context of LRG1


Regulatory relationships of LRG1

  • (3) The lrg1 mutant shows enhanced activity of the Pkc1p pathway [4].
  • Lrg1p-GAP domain strongly and specifically stimulated the GTPase activity of Rho1p, a regulator of beta(1-3)-glucan synthase in vitro. beta(1-3)-glucan deposition was increased in lrg1Delta strains and mislocalized to the tip of the mating projection in fus2Delta strains [3].
  • Additional glucan at the bud site inhibited separation of lrg1 mutants as the clustered phenotype was repressed by expression of the glucanases ENG1 or EGT2 [5].

Other interactions of LRG1

  • Mutations in the LRG1 gene restore impaired 1,3-beta-glucan synthesis in the fks1-1154 Deltafks2 mutant as well as that in rho1-2, a temperature-sensitive mutant of Rho-type GTPase that functions as a regulatory subunit of GS [6].
  • Pairwise combination of mutations in all these genes showed that the simultaneous deletion of SAC7 and LRG1 is synthetically lethal [4].
  • Among eight potential yeast RhoGAPs, Lrg1p is the only member that negatively regulates GS activity: mutations in the rest of GAPs, including bem2, Deltabem3, Deltasac7, Deltabag7, Deltarga1, Deltarga2 and Deltargd1, do not suppress impairment of 1,3-beta-glucan synthesis [6].
  • Functional characterization of the Bag7, Lrg1 and Rgd2 RhoGAP proteins from Saccharomyces cerevisiae [7].

Analytical, diagnostic and therapeutic context of LRG1


  1. LRG1 is expressed during sporulation in Saccharomyces cerevisiae and contains motifs similar to LIM and rho/racGAP domains. Müller, L., Xu, G., Wells, R., Hollenberg, C.P., Piepersberg, W. Nucleic Acids Res. (1994) [Pubmed]
  2. The Cdc34/SCF Ubiquitination Complex Mediates Saccharomyces cerevisiae Cell Wall Integrity. Varelas, X., Stuart, D., Ellison, M.J., Ptak, C. Genetics (2006) [Pubmed]
  3. Lrg1p Is a Rho1 GTPase-activating protein required for efficient cell fusion in yeast. Fitch, P.G., Gammie, A.E., Lee, D.J., de Candal, V.B., Rose, M.D. Genetics (2004) [Pubmed]
  4. Lrg1p functions as a putative GTPase-activating protein in the Pkc1p-mediated cell integrity pathway in Saccharomyces cerevisiae. Lorberg, A., Schmitz, H.P., Jacoby, J.J., Heinisch, J.J. Mol. Genet. Genomics (2001) [Pubmed]
  5. Disruption of LRG1 inhibits mother-daughter separation in Saccharomyces cerevisiae. Svarovsky, M.J., Palecek, S.P. Yeast (2005) [Pubmed]
  6. Yeast Lrg1p acts as a specialized RhoGAP regulating 1,3-beta-glucan synthesis. Watanabe, D., Abe, M., Ohya, Y. Yeast (2001) [Pubmed]
  7. Functional characterization of the Bag7, Lrg1 and Rgd2 RhoGAP proteins from Saccharomyces cerevisiae. Roumanie, O., Weinachter, C., Larrieu, I., Crouzet, M., Doignon, F. FEBS Lett. (2001) [Pubmed]
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