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Gene Review

IRA1  -  Ira1p

Saccharomyces cerevisiae S288c

Synonyms: GLC1, Inhibitory regulator protein IRA1, PPD1, YBR1016, YBR140C
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Disease relevance of IRA1

  • These results suggest that there is a family of sequence-related GAP proteins, which to date includes ras GAP and its yeast counterparts IRA1 and IRA2, rho GAP and the Neurofibromatosis gene product NF1 [1].

High impact information on IRA1


Biological context of IRA1

  • Diploids homozygous for the disrupted IRA1 gene were deficient in sporulation [7].
  • We have identified eight Schizosaccharomyces pombe cDNAs that, when overexpressed, suppress the HS-sensitive phenotype associated with the deletion of IRA1 in S. cerevisiae [8].
  • To identify other genes involved in this pathway, we screened yeast genomic DNA libraries for genes that can suppress the heat shock sensitivity of the ira1 mutation on a multicopy vector [9].
  • The ira1- cells harboring these plasmids retained their HS-sensitive phenotype [8].
  • The sequence of 12.5 kb from the right arm of chromosome II predicts a new N-terminal sequence for the IRA1 protein and reveals two new genes, one of which is a DEAD-box helicase [10].

Associations of IRA1 with chemical compounds

  • Deletion of the Ras-GAPs IRA2 (alone or with IRA1) or the presence of RAS2Val19 allele causes constitutively high Ras GTP loading that no longer increases upon glucose addition [11].
  • Deletion of IRA1 leads to constitutive activation of the Ras/cyclic AMP (cAMP) pathway, which results in several phenotypes including sensitivity to heat-shock (HS) treatment [8].
  • Mutation at the GLC1 locus in Saccharomyces cerevisiae resulted in simultaneous deficiencies in glycogen and trehalose accumulation [12].
  • Similar studies employing a strain containing the glc1 mutation, which enhances porphyrin accumulation, did not reveal any significant phenotypic change in catabolite regulation of 5-aminolevulinate dehydratase [13].
  • Constructed strains containing both glc1 and the constitutive maltose fermentation gene MAL4c can accumulate trehalose but not glycogen during growth on glucose [14].

Regulatory relationships of IRA1

  • The region homologous between the IRA1 protein and ras GTPase-activating protein is also conserved in IRA2 [9].
  • Interactions between adenylate cyclase and the yeast GTPase-activating protein IRA1 [15].

Other interactions of IRA1

  • We identified IRA2, encoding a protein of 3,079 amino acids, that is 45% identical to the IRA1 protein [9].
  • Our results suggest that the IRA1 protein inhibits the function of the RAS proteins in a fashion antagonistic to the function of the CDC25 protein in the RAS-cyclic AMP pathway in Saccharomyces cerevisiae [7].
  • We have identified MSI2 as a gene of Saccharomyces cerevisiae which, when on a multicopy vector, suppresses the heat shock sensitivity caused by the loss of the IRA1 product, a negative regulator of the RAS protein [16].
  • MSI1 is a multicopy suppressor of a mutation in the IRA1 gene involved in the Ras-cAMP pathway that regulates cellular growth [17].
  • We have concluded that IRA1 is a strong candidate for a protein involved in anchoring adenylate cyclase to the membrane [15].


  1. Purification and N-terminal sequence of the p21rho GTPase-activating protein, rho GAP. Garrett, M.D., Major, G.N., Totty, N., Hall, A. Biochem. J. (1991) [Pubmed]
  2. Genetic and epigenetic regulation of the FLO gene family generates cell-surface variation in yeast. Halme, A., Bumgarner, S., Styles, C., Fink, G.R. Cell (2004) [Pubmed]
  3. S. cerevisiae genes IRA1 and IRA2 encode proteins that may be functionally equivalent to mammalian ras GTPase activating protein. Tanaka, K., Nakafuku, M., Satoh, T., Marshall, M.S., Gibbs, J.B., Matsumoto, K., Kaziro, Y., Toh-e, A. Cell (1990) [Pubmed]
  4. The neurofibromatosis type 1 gene encodes a protein related to GAP. Xu, G.F., O'Connell, P., Viskochil, D., Cawthon, R., Robertson, M., Culver, M., Dunn, D., Stevens, J., Gesteland, R., White, R. Cell (1990) [Pubmed]
  5. Genetic analysis of mammalian GAP expressed in yeast. Ballester, R., Michaeli, T., Ferguson, K., Xu, H.P., McCormick, F., Wigler, M. Cell (1989) [Pubmed]
  6. The kelch proteins Gpb1 and Gpb2 inhibit Ras activity via association with the yeast RasGAP neurofibromin homologs Ira1 and Ira2. Harashima, T., Anderson, S., Yates, J.R., Heitman, J. Mol. Cell (2006) [Pubmed]
  7. IRA1, an inhibitory regulator of the RAS-cyclic AMP pathway in Saccharomyces cerevisiae. Tanaka, K., Matsumoto, K., Toh-E, A. Mol. Cell. Biol. (1989) [Pubmed]
  8. Identification and genetic analysis of Schizosaccharomyces pombe cDNAs that suppress deletion of IRA1 in Saccharomyces cerevisiae. Matviw, H., Yu, G., Young, D. Gene (1993) [Pubmed]
  9. IRA2, a second gene of Saccharomyces cerevisiae that encodes a protein with a domain homologous to mammalian ras GTPase-activating protein. Tanaka, K., Nakafuku, M., Tamanoi, F., Kaziro, Y., Matsumoto, K., Toh-e, A. Mol. Cell. Biol. (1990) [Pubmed]
  10. The sequence of 12.5 kb from the right arm of chromosome II predicts a new N-terminal sequence for the IRA1 protein and reveals two new genes, one of which is a DEAD-box helicase. Zagulski, M., Bécam, A.M., Grzybowska, E., Lacroute, F., Migdalski, A., Slonimski, P.P., Sokolowska, B., Herbert, C.J. Yeast (1994) [Pubmed]
  11. Activation state of the Ras2 protein and glucose-induced signaling in Saccharomyces cerevisiae. Colombo, S., Ronchetti, D., Thevelein, J.M., Winderickx, J., Martegani, E. J. Biol. Chem. (2004) [Pubmed]
  12. Regulation of yeast trehalase by a monocyclic, cyclic AMP-dependent phosphorylation-dephosphorylation cascade system. Ortiz, C.H., Maia, J.C., Tenan, M.N., Braz-Padrão, G.R., Mattoon, J.R., Panek, A.D. J. Bacteriol. (1983) [Pubmed]
  13. In situ assay for 5-aminolevulinate dehydratase and application to the study of a catabolite repression-resistant Saccharomyces cerevisiae mutant. Borralho, L.M., Panek, A.D., Malamud, D.R., Sanders, H.K., Mattoon, J.R. J. Bacteriol. (1983) [Pubmed]
  14. Regulation of energy metabolism in yeast. Inheritance of a pleiotropic mutation causing defects in metabolism of energy reserves, ethanol utilization and formation of cytochrome a.a3. Padrão, G.R., Malamud, D.R., Panek, A.D., Mattoon, J.R. Mol. Gen. Genet. (1982) [Pubmed]
  15. Interactions between adenylate cyclase and the yeast GTPase-activating protein IRA1. Mitts, M.R., Bradshaw-Rouse, J., Heideman, W. Mol. Cell. Biol. (1991) [Pubmed]
  16. Isolation of a CDC25 family gene, MSI2/LTE1, as a multicopy suppressor of ira1. Shirayama, M., Matsui, Y., Tanaka, K., Toh-e, A. Yeast (1994) [Pubmed]
  17. A conserved family of WD-40 proteins binds to the retinoblastoma protein in both plants and animals. Ach, R.A., Taranto, P., Gruissem, W. Plant Cell (1997) [Pubmed]
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