the long-term objective of the proposed research is to elucidate the mechanisms that regulate the exit from mitosis in the fission yeast Schizosaccharomyces pombe. The isolation and characterization of the fission yeast dcd1-1ts mutant has led to the identification of two evolutionarily conserved proteins that are required for the complex structural changes associated with the completion of mitosis and re- establishment of the interphase state (Sazer and Nurse, 1992. The dcd1 gene encodes a protein similar to the human chromatin binding protein RCC1. A suppressor of dcd1-1ts, called fyt1, is nearly identical to a human GTP-binding protein in the family typified by the human proto- oncogene p21ras. The similarity of these two S. pombe proteins to human proteins of known function, and in the case of p21ras of known structure as well, provide a framework within which to design experiments examining the role of these and related proteins in mitotic exit. The knowledge gained from the proposed research should further our understanding of the role these human proteins play in cell cycle control, signal transduction pathways, and ras-mediated cancer. The dcd1 and fyt1 proteins are the core of a molecular switch that plays a key role in chromosome decondensation (Sazer & Nurse, 1992). the proposed research is aimed at understanding what turns this switch on and off and what happens when the switch is flipped. The four Specific Aims of the proposed research are to: A) Characterize cell cycle stage specific changes in the behavior of dcd1 and fyt1 proteins. Antibodies to these two proteins will be used to monitor cell cycle changes in their intracellular distribution and their association with the chromatin and each other; B) Identify the proteins that convey the signal for the completion of mitosis to dcd1. Genetic screens will be used to isolate both extragenic suppressors of dcd1-1ts and additional mutants with the dcd1-1ts phenotype; C) Identify proteins that are the effectors of fyt1 and/or the activators of fyt1 GTPase activity. Mutations will be introduced into the fyt1 gene in regions comparable to those in p21ras that are known to be important for effector interaction and for nucleotide binding and hydrolysis. Aberrant phenotypes of cells expressing these genes will be characterized and extragenic suppressors isolated; D) Isolate additional mutants defective in the ability to re-enter the cell cycle following mitosis. The pilot screen in which the dcd1-1ts mutant was identified will be continued to isolate new mutants defective in the mitosis-to-interphase transition.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM049119-05
Application #
2415188
Study Section
Cellular Biology and Physiology Subcommittee 1 (CBY)
Project Start
1993-05-01
Project End
1998-04-30
Budget Start
1997-05-01
Budget End
1998-04-30
Support Year
5
Fiscal Year
1997
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
Chang, Fred; Re, Fabio; Sebastian, Sarah et al. (2004) HIV-1 Vpr induces defects in mitosis, cytokinesis, nuclear structure, and centrosomes. Mol Biol Cell 15:1793-801
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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
Salus, Sandra S; Demeter, Janos; Sazer, Shelley (2002) The Ran GTPase system in fission yeast affects microtubules and cytokinesis in cells that are competent for nucleocytoplasmic protein transport. Mol Cell Biol 22:8491-505
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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