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Mms4, a putative transcriptional (co)activator, protects Saccharomyces cerevisiae cells from endogenous and
1Department of Microbiology, University of Saskatchewan, Saskatoon, Canada. xiaow@sask.usask.ca
Abstract:
mms4-1 is one of several Saccharomyces cerevisiae mutants that exhibit an increased sensitivity to methyl methanesulfonate (MMS), but not to UV or X-rays. We have isolated the MMS4 gene by functional complementation of the MMS-sensitive phenotype in the mms4-1 strain. The MMS4 gene encodes a 691-amino acid, 78.7-kDa protein. The deduced Mms4 protein does not show significant homology to any of the known proteins in the database. However, several putative functional domains suggest that it may be a nuclear protein capable of interacting with other proteins. Examination of the mms4delta mutant phenotype indicates that the mutation not only sensitizes DNA to methylating and ethylating agents, but also to other DNA damage that blocks DNA replication. However, the mms4delta mutant appears to be more sensitive to chronic treatment than to acute treatment by DNA-damaging agents. Furthermore, the spontaneous mutation rate increases significantly in the mms4delta mutant. Mms4 alone, when fused to a Gal4 DNA-binding domain, is able to activate P(GAL1)-lacZ and P(GAL1)-HIS3 reporter genes in a two-hybrid system; the Mms4 transactivation domain maps to the highly acidic N-terminal region. These results collectively suggest that Mms4 may function as a transcriptional (co)activator and play an important role in DNA repair and/or synthesis.
Insights
The MMS4 gene in Saccharomyces cerevisiae is crucial for DNA repair and transcriptional activation. Its absence increases sensitivity to DNA damage and elevates mutation rates, highlighting its role in maintaining genomic stability.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Saccharomyces cerevisiae mutants like mms4-1 show heightened sensitivity to methyl methanesulfonate (MMS).
- Understanding DNA repair mechanisms is vital for genomic stability and disease prevention.
Purpose of the Study:
- To isolate and characterize the MMS4 gene responsible for methyl methanesulfonate sensitivity.
- To elucidate the function of the Mms4 protein in DNA repair and transcriptional regulation.
Main Methods:
- Functional complementation of the MMS-sensitive mms4-1 mutant strain.
- Gene sequencing and protein homology analysis.
- Yeast two-hybrid system to assess transcriptional activation capabilities.
Main Results:
- The MMS4 gene was isolated, encoding a novel 78.7-kDa nuclear protein.
- mms4delta mutants exhibit increased sensitivity to DNA damaging agents and a higher spontaneous mutation rate.
- Mms4 protein possesses a transactivation domain, suggesting a role in transcriptional regulation.
Conclusions:
- Mms4 functions as a transcriptional (co)activator.
- Mms4 plays a significant role in DNA repair and/or DNA synthesis pathways.
- The study provides insights into the molecular mechanisms underlying DNA damage response in yeast.