Potent DNA strand annealing activity associated with mouse Mcm2∼7 heterohexameric complex. Issue 11 (25th April 2017)

• Record Type: Journal Article
• Authors: You, Zhiying; Masai, Hisao
• Is Part Of: Nucleic acids research. Volume 45:Issue 11(2017)
• Page Start: 6494
• Page End: 6506
• Publication Date: 2017-04-25
• Subjects: Nucleic acids -- Periodicals; Molecular biology -- Periodicals; 572.805
• DOI: 10.1093/nar/gkx269
• Languages: English
• ISSNs: 0305-1048

Abstract

Abstract: Mini-chromosome maintenance (Mcm) is a central component for DNA unwinding reaction during eukaryotic DNA replication. Mcm2∼7, each containing a conserved ATPase motif, form a six subunit-heterohexamer. Although the reconstituted Mcm2∼7–Cdc45–GINS (CMG) complex displays DNA unwinding activity, the Mcm2∼7 complex does not generally exhibit helicase activity under a normal assay condition. We detected a strong DNA strand annealing activity in the purified mouse Mcm2∼7 heterohexamer, which promotes rapid reassociation of displaced complementary single-stranded DNAs, suggesting a potential cause for its inability to exhibit DNA helicase activity. Indeed, DNA unwinding activity of Mcm2∼7 could be detected in the presence of a single-stranded DNA that is complementary to the displaced strand, which would prevent its reannealing to the template. ATPase-deficient mutations in Mcm2, 4, 5 and 6 subunits inactivated the annealing activity, while those in Mcm2 and 5 subunits alone did not. The annealing activity of Mcm2∼7 does not require Mg 2+ and ATP, and is adversely inhibited by the presence of high concentration of Mg 2+ and ATP while activated by similar concentrations of ADP. Our findings show that the DNA helicase activity of Mcm2∼7 may be masked by its unexpectedly strong annealing activity, and suggest potential physiological roles of strand annealing activity of Mcm during replication stress responses.