The long term objective of the proposed research is to elucidate the mechanism by which the morphological changes required for the mitosis to interphase transition are regulated. Because of its excellent genetics and cytology, fission yeast is an excellent experimental system in which to study this point in the cell cycle at which the chromosomes decondense, the nuclear envelope reforms around the chromosomes, and the cells undergo cytokinesis and separate from one another. The focus of this proposal is on spi1, the evolutionarily conserved GTPase that is essential for the mitosis to interphase transition in fission yeast. spi1 is nearly identical to the human proto-oncogene p21ras in its GTP binding and hydrolysis domains, and its regulators are also evolutionarily conserved. The proposed studies will further our understanding of the function of this eukaryotic GTPase in particular, and the findings will be applicable to studies of the large family of structurally related GTPases that regulate a wide variety of cellular functions, and to the elucidation of the mechanism by which GTPases interact with their downstream targets via the activation of signal transduction pathways. Perturbations in the GTPase cycle, leading to an accumulation of either the GTP- or GDP-bound forms, have similar, easily monitored phenotypic consequences. This observation led to the generation of a collection of genes and mutants that based on a variety of criteria are likely to identify regulators and downstream targets of the spi1 GTPase. The proposed genetic, phenotypic, and biochemical analyses will elucidate their relationship to the known components of the spi1 GTPase system.
The Specific Aims of this proposal are:
SPECIFIC AIM I. Identify targets of the spi1 GTPase by characterizing the sns mutants and the med genes that interact genetically with components of the GTPase system;
SPECIFIC AIM II. Identify targets of the spi1 GTPase by isolating genes that when overproduced can rescue the temperature sensitive lethality of the pim1-d1 mutuant; and SPEICIFIC AIM III. Test the hypothesis that the nuclear envelope is a downstream target of the spi1 GTPase system.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM049119-07
Application #
2910119
Study Section
Cellular Biology and Physiology Subcommittee 1 (CBY)
Project Start
1993-05-01
Project End
2002-04-30
Budget Start
1999-05-01
Budget End
2000-04-30
Support Year
7
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Baylor College of Medicine
Department
Biochemistry
Type
Schools of Medicine
DUNS #
074615394
City
Houston
State
TX
Country
United States
Zip Code
77030
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Kadura, Sheila; He, Xiangwei; Vanoosthuyse, Vincent et al. (2005) The A78V mutation in the Mad3-like domain of Schizosaccharomyces pombe Bub1p perturbs nuclear accumulation and kinetochore targeting of Bub1p, Bub3p, and Mad3p and spindle assembly checkpoint function. Mol Biol Cell 16:385-95
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Bai, Siau Wei; Rouquette, Jacques; Umeda, Makoto et al. (2004) The fission yeast Nup107-120 complex functionally interacts with the small GTPase Ran/Spi1 and is required for mRNA export, nuclear pore distribution, and proper cell division. Mol Cell Biol 24:6379-92
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Matynia, Anna; Salus, Sandra S; Sazer, Shelley (2002) Three proteins required for early steps in the protein secretory pathway also affect nuclear envelope structure and cell cycle progression in fission yeast. J Cell Sci 115:421-31
Fleig, U; Salus, S S; Karig, I et al. (2000) The fission yeast ran GTPase is required for microtubule integrity. J Cell Biol 151:1101-11
He, X; Jones, M H; Winey, M et al. (1998) 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 111 ( Pt 12):1635-47
Demeter, J; Sazer, S (1998) imp2, a new component of the actin ring in the fission yeast Schizosaccharomyces pombe. J Cell Biol 143:415-27

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