Minichromosome Maintenance as a Genetic Assay for Defects in DNA Replication

Minichromosome maintenance (mcm) is an effective genetic assay for mutants defective in DNA replication. Two classes of mcm mutants have been identified using this screen: those that differentially affect the activities of certain autonomously replicating sequences (ARSs) and those that uniformly affect the activities of all ARSs. The ARS-specific MCM genes are essential for the initiation of DNA replication. Among these are members of the MCM2-7 family that encode subunits of the preinitiation complex and MCM10, whose gene product interacts with members of the Mcm2-7 proteins. Among the ARSnonspecific MCM gene products are chromosome transmission factors. Refinement of this genetic assay as a screening tool and further analysis of existing mcm mutants may reveal new replication initiation proteins.