The Identification of cDNAs That Affect the Mitosis-to-Interphase Transition in Schizosaccharomyces pombe, Including sbp1, Which Encodes a spi1p-GTP–Binding Protein

Corresponding author: Shelley Sazer, Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, ssazer{at}bcm.tmc.edu (E-mail).

Communicating editor: F. WINSTON

Perturbations of the spi1p GTPase system in fission yeast, caused by mutation or overexpression of several regulatory proteins, result in a unique terminal phenotype that includes condensed chromosomes, a wide medial septum, and a fragmented nuclear envelope. To identify potential regulators or targets of the spi1p GTPase system, a screen for cDNAs whose overexpression results in this terminal phenotype was conducted, and seven clones that represent three genes, named med1, med2, and med3 (mitotic exit defect), were identified. Their genetic interaction with the spi1p GTPase system was established by showing that the spi1p guanine nucleotide exchange factor mutant pim1-d1^ts was hypersensitive to their overexpression. med1 encodes a homologue of the human Ran-binding protein, RanBP1, and has been renamed sbp1 (spi1-binding protein). sbp1p binds to spi1p-GTP and costimulates the GTPase-activating protein (GAP)-catalyzed GTPase activity. Cells in which sbp1p is depleted or overproduced phenocopy cells in which the balance between spi1p-GTP and spi1p-GDP is perturbed by other means. Therefore, sbp1p mediates and/or regulates the essential functions of the spi1p GTPase system. med2 and med3 encode novel fission yeast proteins that, based on our phenotypic analyses, are likely to identify additional regulators or effectors of the spi1p GTPase system.

This article has been cited by other articles:

				A. L. Dawe, V. C. McMains, M. Panglao, S. Kasahara, B. Chen, and D. L. Nuss An ordered collection of expressed sequences from Cryphonectria parasitica and evidence of genomic microsynteny with Neurospora crassa and Magnaporthe grisea Microbiology, September 1, 2003; 149(9): 2373 - 2384. [Abstract] [Full Text] [PDF]

				S. S. Salus, J. Demeter, and S. Sazer The Ran GTPase System in Fission Yeast Affects Microtubules and Cytokinesis in Cells That Are Competent for Nucleocytoplasmic Protein Transport Mol. Cell. Biol., December 15, 2002; 22(24): 8491 - 8505. [Abstract] [Full Text] [PDF]

				G. Timinszky, L. Tirian, F. T. Nagy, G. Toth, A. Perczel, Z. Kiss-Laszlo, I. Boros, P. R. Clarke, and J. Szabad The importin-{beta} P446L dominant-negative mutant protein loses RanGTP binding ability and blocks the formation of intact nuclear envelope J. Cell Sci., April 15, 2002; 115(8): 1675 - 1687. [Abstract] [Full Text] [PDF]

				K. Tatebayashi, T. Tani, and H. Ikeda Fission Yeast Mog1p Homologue, Which Interacts With the Small GTPase Ran, Is Required for Mitosis-to-Interphase Transition and poly(A)+ RNA Metabolism Genetics, April 1, 2001; 157(4): 1513 - 1522. [Abstract] [Full Text]

				U. Fleig, S. S. Salus, I. Karig, and S. Sazer The Fission Yeast Ran GTPase Is Required for Microtubule Integrity J. Cell Biol., November 20, 2000; 151(5): 1101 - 1112. [Abstract] [Full Text] [PDF]

				G. Guarguaglini, L. Renzi, F. D’Ottavio, B. Di Fiore, M. Casenghi, E. Cundari, and P. Lavia Regulated Ran-binding Protein 1 Activity Is Required for Organization and Function of the Mitotic Spindle in Mammalian Cells in Vivo Cell Growth Differ., August 1, 2000; 11(8): 455 - 465. [Abstract] [Full Text]

				I. Novoa, M. G. Rush, and P. D'Eustachio Isolated Mammalian and Schizosaccharomyces pombe Ran-binding Domains Rescue S. pombe sbp1 (RanBP1) Genomic Mutants Mol. Biol. Cell, July 1, 1999; 10(7): 2175 - 2190. [Abstract] [Full Text]

				M. K. Balasubramanian, D. McCollum, L. Chang, K. C. Y. Wong, N. I. Naqvi, X. He, S. Sazer, and K. L. Gould Isolation and Characterization of New Fission Yeast Cytokinesis Mutants Genetics, July 1, 1998; 149(3): 1265 - 1275. [Abstract] [Full Text] [PDF]

				A. Matynia, U. Mueller, N. Ong, J. Demeter, A. L. Granger, K. Hinata, and S. Sazer Isolation and Characterization of Fission Yeast sns Mutants Defective at the Mitosis-to-Interphase Transition Genetics, April 1, 1998; 148(4): 1799 - 1811. [Abstract] [Full Text] [PDF]

				X He, M. Jones, M Winey, and S Sazer Mph1, a member of the Mps1-like family of dual specificity protein kinases, is required for the spindle checkpoint in S. pombe J. Cell Sci., January 6, 1998; 111(12): 1635 - 1647. [Abstract] [PDF]