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Gene Review

RSR1  -  Ras family GTPase RSR1

Saccharomyces cerevisiae S288c

Synonyms: BUD1, G6658, Ras-related protein RSR1, YGR152C
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High impact information on RSR1

  • We have identified a gene, BUD5, that resembles BUD1 and BUD2 in being required for both patterns; bud5- mutants also exhibit random budding in all cell types [1].
  • We have identified four genes, BUD1-BUD4, necessary for the axial pattern by isolating mutants of alpha cells that do not exhibit this pattern [2].
  • Mutants defective in BUD1, BUD2 or BUD5 choose bud sites randomly [3].
  • Here we report that Bud2p is a GTPase-activating protein (GAP) for Bud1p with a sequence similar to the catalytic domain of rasGAPs, and that Bud2p purified from yeast stimulates GTP hydrolysis by Bud1p [3].
  • Furthermore, the simultaneous disruption of RAS1, RAS2, and the RAS-related gene RSR1 was lethal at any temperature [4].

Biological context of RSR1


Anatomical context of RSR1

  • Like Ras, Bud1p GTPase is constitutively associated with the plasma membrane; however, concentrated activities of Bud5p GDP-GTP exchange factor and Bud2p GTPase-activating protein at the future bud site promote rapid cycling of Bud1p between GTP- and GDP-bound conformations in a spatially restricted manner [8].
  • Consistent with this hypothesis, we found an Rsr1p-specific GTPase-activating protein (GAP) activity in yeast membranes which was not active toward p21rap1A, indicating that p21rap1A may be predominantly GTP bound in yeast cells [9].
  • In this paper we demonstrate that the intrinsic GTPase activity of the Rsr1 protein is stimulated by GAP3 purified from bovine brain cytosol [10].
  • Surprisingly, Rsr1/Bud1 also localized to intracellular membranes [11].
  • Similarly, in activated neutrophils, the NADPH oxidase is found in a complex with rap1, the mammalian homologue of BUD1 (BoKoch et al., 1989) [12].

Associations of RSR1 with chemical compounds


Physical interactions of RSR1

  • We also show that Cdc42p coimmunoprecipitated with Rsr1p/Bud1p from yeast extracts [13].
  • Rsr1p/Bud1p binds to the CH-domain of Cdc24p, which is essential for its function in vivo [14].
  • It seems likely, therefore, that the target is not simply a plasma-membrane protein but may be a complex of proteins whose formation is under the control of the rap1/BUD1 GTPase [12].

Regulatory relationships of RSR1

  • Rsr1p/Bud1p appears to activate the GEF activity of Cdc24p in vivo, possibly by triggering a conformational change that dissociates the PB1-domain from its intramolecular binding site [14].
  • Although Rap1-specific GAP stimulated the GTPase of Rsr1p in vitro, it did not dominantly interfere with Rsr1p function in vivo [9].
  • The relative timing of Bud5 and Bud2 localizations suggests that both regulators contribute to the spatially specific control of Bud1 GTPase [15].

Other interactions of RSR1

  • The RSR1 gene, which was previously identified as a multicopy suppressor of Ts- mutations in the bud-emergence gene CDC24, encodes a GTPase of the Ras family that is required for both budding patterns [16].
  • Here we show specific genetic interactions between RSR1/BUD1 and particular cdc42 mutants defective in polarity establishment [13].
  • RESULTS: Here we show that a rsr1 gic1 gic2 mutant fails to initiate budding, resulting in unbudded, large, and multinucleated cells [17].
  • This suppression by BUD5 can be reversed by simultaneous overexpression of RNA1, and is not Rsr1p-dependent, nor allele-specific [18].
  • Bud formation in yeast involves the actions of the Ras-type GTPase Rsr1, which is required for the proper selection of the bud site, and the Rho-type GTPase Cdc42, which is necessary for the assembly of cytoskeletal structures at that site [19].

Analytical, diagnostic and therapeutic context of RSR1


  1. Yeast BUD5, encoding a putative GDP-GTP exchange factor, is necessary for bud site selection and interacts with bud formation gene BEM1. Chant, J., Corrado, K., Pringle, J.R., Herskowitz, I. Cell (1991) [Pubmed]
  2. Genetic control of bud site selection in yeast by a set of gene products that constitute a morphogenetic pathway. Chant, J., Herskowitz, I. Cell (1991) [Pubmed]
  3. BUD2 encodes a GTPase-activating protein for Bud1/Rsr1 necessary for proper bud-site selection in yeast. Park, H.O., Chant, J., Herskowitz, I. Nature (1993) [Pubmed]
  4. Requirement of Saccharomyces cerevisiae Ras for completion of mitosis. Morishita, T., Mitsuzawa, H., Nakafuku, M., Nakamura, S., Hattori, S., Anraku, Y. Science (1995) [Pubmed]
  5. A role for a protease in morphogenic responses during yeast cell fusion. Elia, L., Marsh, L. J. Cell Biol. (1998) [Pubmed]
  6. Multicopy suppression of the cdc24 budding defect in yeast by CDC42 and three newly identified genes including the ras-related gene RSR1. Bender, A., Pringle, J.R. Proc. Natl. Acad. Sci. U.S.A. (1989) [Pubmed]
  7. A GDP/GTP exchange factor involved in linking a spatial landmark to cell polarity. Kang, P.J., Sanson, A., Lee, B., Park, H.O. Science (2001) [Pubmed]
  8. A mechanism of Bud1p GTPase action suggested by mutational analysis and immunolocalization. Michelitch, M., Chant, J. Curr. Biol. (1996) [Pubmed]
  9. Functional interaction between p21rap1A and components of the budding pathway in Saccharomyces cerevisiae. McCabe, P.C., Haubruck, H., Polakis, P., McCormick, F., Innis, M.A. Mol. Cell. Biol. (1992) [Pubmed]
  10. Rsr1 and Rap1 GTPases are activated by the same GTPase-activating protein and require threonine 65 for their activation. Holden, J.L., Nur-E-Kamal, M.S., Fabri, L., Nice, E., Hammacher, A., Maruta, H. J. Biol. Chem. (1991) [Pubmed]
  11. Localization of the Rsr1/Bud1 GTPase involved in selection of a proper growth site in yeast. Park, H.O., Kang, P.J., Rachfal, A.W. J. Biol. Chem. (2002) [Pubmed]
  12. Ras-related GTPases and the cytoskeleton. Hall, A. Mol. Biol. Cell (1992) [Pubmed]
  13. Interaction between a Ras and a Rho GTPase couples selection of a growth site to the development of cell polarity in yeast. Kozminski, K.G., Beven, L., Angerman, E., Tong, A.H., Boone, C., Park, H.O. Mol. Biol. Cell (2003) [Pubmed]
  14. The nucleotide exchange factor Cdc24p may be regulated by auto-inhibition. Shimada, Y., Wiget, P., Gulli, M.P., Bi, E., Peter, M. EMBO J. (2004) [Pubmed]
  15. A localized GTPase exchange factor, Bud5, determines the orientation of division axes in yeast. Marston, A.L., Chen, T., Yang, M.C., Belhumeur, P., Chant, J. Curr. Biol. (2001) [Pubmed]
  16. Genetic evidence for the roles of the bud-site-selection genes BUD5 and BUD2 in control of the Rsr1p (Bud1p) GTPase in yeast. Bender, A. Proc. Natl. Acad. Sci. U.S.A. (1993) [Pubmed]
  17. The upstream regulator, Rsr1p, and downstream effectors, Gic1p and Gic2p, of the Cdc42p small GTPase coordinately regulate initiation of budding in Saccharomyces cerevisiae. Kawasaki, R., Fujimura-Kamada, K., Toi, H., Kato, H., Tanaka, K. Genes Cells (2003) [Pubmed]
  18. Overexpression of Bud5p can suppress mutations in the Gsp1p guanine nucleotide exchange factor Prp20p in Saccharomyces cerevisiae. Clément, M., Lavallée, F., Barbès-Morin, G., de Repentigny, L., Belhumeur, P. Mol. Genet. Genomics (2001) [Pubmed]
  19. Interactions among proteins involved in bud-site selection and bud-site assembly in Saccharomyces cerevisiae. Zheng, Y., Bender, A., Cerione, R.A. J. Biol. Chem. (1995) [Pubmed]
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