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Two mcm3 mutations affect different steps in the initiation of DNA replication.
Ming Lei1, Irene H Cheng, Louis A Roberts
1Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, WI 53226, USA. mlei@mcw.edu
The Journal of Biological Chemistry
|June 13, 2002
Summary
Two DNA replication mutants in yeast, mcm3-1 and mcm3-10, reveal distinct defects in replication initiation. Mcm3-10 impairs MCM complex recruitment, while Mcm3-1 affects initiation efficiency post-recruitment.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- The MCM2-7 complex is essential for eukaryotic DNA replication initiation and elongation.
- Mcm3 is a critical subunit of the MCM2-7 complex.
- Understanding Mcm3 function is key to deciphering replication control.
Purpose of the Study:
- To characterize two Saccharomyces cerevisiae Mcm3 mutant alleles, mcm3-1 and mcm3-10.
- To determine the specific defects in DNA replication initiation caused by these mutations.
Main Methods:
- Genetic analysis of mcm3-1 and mcm3-10 mutant alleles in yeast.
- Biochemical assays to assess Mcm3 interactions and MCM complex recruitment to origins.
- Comparison with previously characterized mutations in Mcm3 and Mcm5.
Main Results:
- Mcm3-10 mutation (P118L) disrupts Mcm3-Mcm5 interaction and MCM complex recruitment to replication origins.
- Mcm3-1 mutation (G246E) reduces replication initiation efficiency but does not affect MCM complex recruitment.
- The P118 residue is conserved and crucial for Mcm3 function.
Conclusions:
- Mcm3-10 is defective in an early step of replication initiation, prior to MCM complex recruitment.
- Mcm3-1 is defective in a later step of replication initiation, after MCM complex recruitment.
- These findings highlight distinct roles for Mcm3 in the temporal regulation of DNA replication initiation.