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Moe1, a conserved protein in Schizosaccharomyces pombe, interacts with a Ras effector, Scd1, to affect proper spindle
1Department of Biology, New York University, 1009 Main Building, 100 Washington Square East, New York, NY 10003-6688, USA.
Abstract:
In fission yeast, Scd1/Ral1 is a putative guanine nucleotide exchange factor for Cdc42sp and also acts as a Ras1 effector necessary for the regulation of cytoskeleton organization. In this study, we have characterized a protein, Moe1, that binds directly to Scd1. A moe1 null (Delta) mutant exhibits numerous phenotypes indicative of abnormal microtubule functioning, including an abnormality in the spindle. moe1Delta mutants are resistant to microtubule destabilizing agents; moreover, moe1Delta rescued the growth defects of tubulin mutants containing unstable microtubules. These results suggest that Moe1 induces instability in microtubules. Biochemical and subcellular localization studies suggest that Moe1 and Scd1 colocalize in the nucleus. Furthermore, loss of function in Scd1 or Ras1 also induced abnormality in the spindle and is synthetically lethal with moe1Delta producing cells that lack a detectable spindle. These data demonstrate that Moe1 is a component of the Ras1 pathway necessary for proper spindle formation in the nucleus. Human and nematode Moe1 both can substitute for yeast Moe1, indicating that the function of Moe1 in spindle formation has been conserved substantially during evolution.
Insights
Moe1 protein is essential for proper spindle formation in fission yeast. Loss of Moe1 leads to microtubule instability and defects in cell division, a function conserved across species.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Scd1/Ral1 is a guanine nucleotide exchange factor for Cdc42sp and a Ras1 effector regulating cytoskeleton organization in fission yeast.
- The precise role of Scd1/Ral1 effectors in nuclear processes like spindle formation remains incompletely understood.
Purpose of the Study:
- To characterize the function of a novel protein, Moe1, which binds to Scd1.
- To investigate Moe1's role in microtubule dynamics and spindle formation within the Ras1 pathway.
Main Methods:
- Characterization of a moe1 null mutant for phenotypic analysis.
- Biochemical assays to confirm protein-protein interactions.
- Subcellular localization studies using microscopy.
- Genetic interaction studies with known pathway components (Scd1, Ras1, tubulin mutants).
Main Results:
- Moe1 directly binds to Scd1 and colocalizes with it in the nucleus.
- Moe1 null mutants display abnormal microtubule function, spindle defects, and resistance to microtubule-destabilizing agents.
- Moe1 loss-of-function rescues growth defects in tubulin mutants with unstable microtubules, suggesting Moe1 induces microtubule instability.
- Loss of Scd1 or Ras1 function also causes spindle abnormalities and is synthetically lethal with moe1 deletion, indicating Moe1 is part of the Ras1 pathway.
- Human and nematode Moe1 proteins can functionally substitute for yeast Moe1.
Conclusions:
- Moe1 is a crucial component of the Ras1 pathway, essential for proper nuclear spindle formation in fission yeast.
- Moe1's function in regulating microtubule stability and spindle formation is conserved throughout evolution.