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Gene Review

USO1  -  Uso1p

Saccharomyces cerevisiae S288c

Synonyms: INT1, Int-1, Intracellular protein transport protein USO1, YDL058W
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Disease relevance of USO1

  • Because the intestinal tract is considered a major portal of entry for systemic candidiasis, experiments were designed to clarify the ability of yeast and filamentous forms, as well as the INT1 gene product, to influence adherence of Candida albicans to the intestinal epithelium [1].

High impact information on USO1

  • Thus, INT1 links adhesion, filamentous growth, and pathogenicity in C. albicans and Int1p may be an attractive target for the development of antifungal therapies [2].
  • INT1 expression in Saccharomyces cerevisiae was sufficient to direct the adhesion of this normally nonadherent yeast to human epithelial cells [2].
  • Glycosylphosphatidylinositol (GPI)-anchored proteins exit the ER in distinct vesicles from other secretory proteins, and this sorting event requires the Rab GTPase Ypt1p, tethering factors Uso1p, and the conserved oligomeric Golgi complex [3].
  • Here, we identified a protein Mid2p on the basis of its sequence similarity to S. pombe Mid1p, Saccharomyces cerevisiae Bud4p, and Candida albicans Int1p [4].
  • Weaker suppression is evident upon overexpression of genes encoding the vesicle tethering factor Uso1p or the vesicle-SNAREs Sec22p, Bet1p, or Ykt6p [5].

Biological context of USO1


Anatomical context of USO1

  • Using a cell-free assay that measures distinct steps in vesicle transport from the ER to the Golgi, we find Sec35p is required for a vesicle docking stage catalyzed by Uso1p [11].
  • ER-to-Golgi transport in yeast may be reproduced in vitro with washed membranes, purified proteins (COPII, Uso1p and LMA1) and energy [9].
  • Purified Sec18p, Uso1p, and LMA1 in the presence of ATP and GTP satisfies the requirement for cytosol in fusion of ER-derived vesicles with Golgi membranes [12].
  • YKR15, which has been recently cloned as the MPL1 gene, encodes a polypeptide that shows homologies to myosin heavy chain and to the cytoskeleton protein Uso1 [13].
  • These results imply that (i) Cdrlp and Ftrlp are transported to the plasma membrane by the general secretory pathway, (ii) Mlt1p enters the secretory pathway but is diverted to the vacuole at an early post-Golgi step, and (iii) like Cdc10p, Int1p does not enter the general secretory pathway [14].

Associations of USO1 with chemical compounds

  • In sucrose density gradient centrifugation, however, the Uso1 protein cosedimented with a globular 6S marker protein, horseradish peroxidase (44 kDa) [7].
  • Interestingly, the Mn(2+) dependence of I-IFG is not dependent upon the presence of the putative divalent cation-binding domains found in INT1 [15].
  • In this study, we found that INT1-induced filamentous growth (I-IFG) is sensitive to the divalent cation chelator EDTA and that this EDTA sensitivity can be ameliorated by the addition of Mn(2+), but not Mg(2+) or Ca(2+) ions [15].

Physical interactions of USO1


Co-localisations of USO1

  • In C. albicans, Int1p was important for the axial budding pattern and colocalized with Cdc3p septin in a ring at the mother-bud neck of yeast and pseudohyphal cells [17].

Other interactions of USO1

  • Finally, we describe RUD3, a novel gene identified through a genetic screen for multicopy suppressors of a mutation in USO1, which suppresses the sec34-2 mutation as well [5].
  • The Rab GTPase Ypt1p and the large homodimer Uso1p are both required for tethering endoplasmic reticulum-derived vesicles to early Golgi compartments in yeast [18].
  • These genetic and biochemical results suggest Sec35p acts with Uso1p to dock ER-derived vesicles to the Golgi complex [11].
  • LMA1 and Sec18p are required for vesicle fusion after Uso1p function [9].
  • Analysis of the derived amino acid sequence demonstrated > 98% identity with the S. cerevisiae protein Uso1p, a myosin-like polypeptide found exclusively in the cytosol [19].

Analytical, diagnostic and therapeutic context of USO1

  • Antibodies raised against partial sequences of the Uso1 polypeptide reacted with a 200 kDa protein in Western blots of the wild-type yeast proteins [7].
  • The Uso1 protein was found predominantly in the soluble fraction and displayed a molecular mass of 800-900 kDa in gel filtration when globular protein were used as molecular mass standards [7].
  • By Southern blotting, alpha INT1 is unique to C. albicans [20].
  • The INT1 gene is associated with enhanced colonization and dissemination in these animal models [21].


  1. Adherence of yeast and filamentous forms of Candida albicans to cultured enterocytes. Wiesner, S.M., Bendel, C.M., Hess, D.J., Erlandsen, S.L., Wells, C.L. Crit. Care Med. (2002) [Pubmed]
  2. Linkage of adhesion, filamentous growth, and virulence in Candida albicans to a single gene, INT1. Gale, C.A., Bendel, C.M., McClellan, M., Hauser, M., Becker, J.M., Berman, J., Hostetter, M.K. Science (1998) [Pubmed]
  3. The ER v-SNAREs are required for GPI-anchored protein sorting from other secretory proteins upon exit from the ER. Morsomme, P., Prescianotto-Baschong, C., Riezman, H. J. Cell Biol. (2003) [Pubmed]
  4. Mid2p stabilizes septin rings during cytokinesis in fission yeast. Berlin, A., Paoletti, A., Chang, F. J. Cell Biol. (2003) [Pubmed]
  5. Sec34p, a protein required for vesicle tethering to the yeast Golgi apparatus, is in a complex with Sec35p. VanRheenen, S.M., Cao, X., Sapperstein, S.K., Chiang, E.C., Lupashin, V.V., Barlowe, C., Waters, M.G. J. Cell Biol. (1999) [Pubmed]
  6. Uso1 protein is a dimer with two globular heads and a long coiled-coil tail. Yamakawa, H., Seog, D.H., Yoda, K., Yamasaki, M., Wakabayashi, T. J. Struct. Biol. (1996) [Pubmed]
  7. Molecular characterization of the USO1 gene product which is essential for vesicular transport in Saccharomyces cerevisiae. Seog, D.H., Kito, M., Igarashi, K., Yoda, K., Yamasaki, M. Biochem. Biophys. Res. Commun. (1994) [Pubmed]
  8. Uso1 protein contains a coiled-coil rod region essential for protein transport from the ER to the Golgi apparatus in Saccharomyces cerevisiae. Seog, D.H., Kito, M., Yoda, K., Yamasaki, M. J. Biochem. (1994) [Pubmed]
  9. Initial docking of ER-derived vesicles requires Uso1p and Ypt1p but is independent of SNARE proteins. Cao, X., Ballew, N., Barlowe, C. EMBO J. (1998) [Pubmed]
  10. Calcium and SLY genes suppress the temperature-sensitive secretion defect of Saccharomyces cerevisiae uso1 mutant. Kito, M., Seog, D.H., Igarashi, K., Kambe-Honjo, H., Yoda, K., Yamasaki, M. Biochem. Biophys. Res. Commun. (1996) [Pubmed]
  11. Sec35p, a novel peripheral membrane protein, is required for ER to Golgi vesicle docking. VanRheenen, S.M., Cao, X., Lupashin, V.V., Barlowe, C., Waters, M.G. J. Cell Biol. (1998) [Pubmed]
  12. Coupled ER to Golgi transport reconstituted with purified cytosolic proteins. Barlowe, C. J. Cell Biol. (1997) [Pubmed]
  13. The complete sequence of a 15,820 bp segment of Saccharomyces cerevisiae chromosome XI contains the UBI2 and MPL1 genes and three new open reading frames. Bou, G., Esteban, P.F., Baladron, V., Gonzalez, G.A., Cantalejo, J.G., Remacha, M., Jimenez, A., Del Rey, F., Ballesta, J.P., Revuelta, J.L. Yeast (1993) [Pubmed]
  14. Intracellular trafficking of fluorescently tagged proteins associated with pathogenesis in Candida albicans. Lee, S.A., Khalique, Z., Gale, C.A., Wong, B. Med. Mycol. (2005) [Pubmed]
  15. Filamentous growth of Saccharomyces cerevisiae is regulated by manganese. Asleson, C.M., Asleson, J.C., Malandra, E., Johnston, S., Berman, J. Fungal Genet. Biol. (2000) [Pubmed]
  16. Assembly of the ER to Golgi SNARE complex requires Uso1p. Sapperstein, S.K., Lupashin, V.V., Schmitt, H.D., Waters, M.G. J. Cell Biol. (1996) [Pubmed]
  17. Candida albicans Int1p interacts with the septin ring in yeast and hyphal cells. Gale, C., Gerami-Nejad, M., McClellan, M., Vandoninck, S., Longtine, M.S., Berman, J. Mol. Biol. Cell (2001) [Pubmed]
  18. A Rab requirement is not bypassed in SLY1-20 suppression. Ballew, N., Liu, Y., Barlowe, C. Mol. Biol. Cell (2005) [Pubmed]
  19. Antigenic and functional conservation of an integrin I-domain in Saccharomyces cerevisiae. Hostetter, M.K., Tao, N.J., Gale, C., Herman, D.J., McClellan, M., Sharp, R.L., Kendrick, K.E. Biochem. Mol. Med. (1995) [Pubmed]
  20. Cloning and expression of a gene encoding an integrin-like protein in Candida albicans. Gale, C., Finkel, D., Tao, N., Meinke, M., McClellan, M., Olson, J., Kendrick, K., Hostetter, M. Proc. Natl. Acad. Sci. U.S.A. (1996) [Pubmed]
  21. Fungal infection in the very low birthweight infant. Kaufman, D. Curr. Opin. Infect. Dis. (2004) [Pubmed]
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