Two mcm3 Mutations Affect Different Steps in the Initiation of DNA Replication

• Published in: The Journal of biological chemistry Vol. 277; no. 34; pp. 30824 - 30831
• Main Authors: Lei, Ming, Cheng, Irene H, Roberts, Louis A, McAlear, Michael A, Tye, Bik K
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 23.08.2002
• Subjects: Alleles; Amino Acid Sequence; Cell Cycle Proteins - physiology; DNA Replication; DNA-Binding Proteins - physiology; Minichromosome Maintenance Complex Component 7; Molecular Sequence Data; Mutation; Nuclear Proteins - physiology; S Phase; Saccharomyces cerevisiae Proteins; Schizosaccharomyces pombe Proteins
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M201816200

Mcm3 is a subunit of the hexameric MCM2-7 complex required for the initiation and elongation of DNA replication in eukaryotes. We have characterized two mutant alleles, mcm3-1 and mcm3-10 , in Saccharomyces cerevisiae and showed that they are defective at different steps of the replication initiation process. Mcm3-10 contains a P118L substitution that compromises its interaction with Mcm5 and the recruitment of Mcm3 and Mcm7 to a replication origin. P118 is conserved between Mcm3, Mcm4, Mcm5, and Mcm7. An identical substitution of this conserved residue in Mcm5 (P83L of mcm5-bob1) strengthens the interaction between Mcm3 and Mcm5 and allows cells to enter S phase independent of Cdc7-Dbf4 kinase (Hardy, C. F., Dryga, O., Pahl, P. M. B., and Sclafani, R. A. (1997) Proc. Natl. Acad. Sci. U. S. A. 94, 3151–3155). Mcm3-1 contains a G246E mutation that diminishes the efficiency of replication initiation (Yan, H., Merchant, A. M., and Tye, B. K. (1993) Genes Dev. 7, 2149–2160) but not its interaction with Mcm5 or recruitment of the MCM2-7 complex to replication origin. These observations indicate that Mcm3-10 is defective in a step before, and Mcm3-1 is defective in a step after the recruitment of the MCM2-7 complex to replication origins.