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A conditional lethal mutant in the fission yeast 26 S protease subunit mts3+ is defective in metaphase to anaphase
C Gordon1, G McGurk, M Wallace
1Medical Research Council Human Genetics Unit, Western General Hospital, Edinburgh, Scotland, United Kingdom.
Abstract:
We have isolated a conditional lethal mutant mts3 in the fission yeast Schizosaccharomyces pombe which at the permissive temperature is resistant to the mitotic poison MBC and at the restrictive temperature is defective in metaphase to anaphase transition. The predicted amino acid sequence of mts3+ is 36% identical with the budding yeast gene NIN1. NIN1 cloned into a fission yeast expression vector can rescue both mts3 temperature-sensitive and null alleles demonstrating that NIN1 is the budding yeast homologue of the fission yeast mts3+ gene. The phenotype of the mts3 null is identical with the mts3 ts mutant demonstrating that the phenotype of the mts3 ts mutant is due to loss of mts3+ function. The deduced amino acid sequences of both mts3+ and NIN1 show homology to peptide sequences obtained from subunit 14 of the 26 S protease purified from bovine or human cells.
Insights
We identified a fission yeast mutant, mts3, crucial for cell division. Its counterpart in budding yeast, NIN1, rescues the defect, revealing a conserved role in cell cycle regulation.
Area of Science:
- Cell Biology
- Genetics
- Molecular Biology
Background:
- The cell cycle involves precise regulation of transitions between phases.
- Mitotic progression requires accurate chromosome segregation.
- Conditional lethal mutants are valuable tools for studying essential genes.
Purpose of the Study:
- To characterize a novel conditional lethal mutant, mts3, in Schizosaccharomyces pombe.
- To identify the homologous gene in budding yeast and elucidate its function.
- To investigate the role of mts3+ in metaphase to anaphase transition.
Main Methods:
- Isolation and characterization of the conditional lethal mutant mts3.
- Complementation analysis using the budding yeast gene NIN1.
- Phenotypic analysis of mts3 temperature-sensitive and null alleles.
- Sequence homology analysis with known proteins.
Main Results:
- The mts3 mutant exhibits resistance to MBC at permissive temperatures and metaphase-anaphase transition defects at restrictive temperatures.
- The budding yeast NIN1 gene rescues both temperature-sensitive and null mts3 alleles.
- NIN1 is the functional homologue of the fission yeast mts3+ gene.
- mts3+ and NIN1 show homology to subunit 14 of the 26S protease.
Conclusions:
- The mts3 gene is essential for proper cell division in Schizosaccharomyces pombe.
- NIN1 is the conserved homologue of mts3+, playing a critical role in cell cycle progression in yeast.
- The conserved function suggests a role in proteasome-dependent processes regulating the cell cycle.