title: Activation of the MCM2-7 helicase by association with Cdc45 and GINS proteins.
abstract: MCM2-7 proteins provide essential helicase functions in eukaryotes at chromosomal DNA replication forks. During the G1 phase of the cell cycle, they remain loaded on DNA but are inactive. We have used recombinant methods to show that the Drosophila MCM2-7 helicase is activated in complex with Cdc45 and the four GINS proteins (CMG complex). Biochemical activities of the MCM AAA+ motor are altered and enhanced through such associations: ATP hydrolysis rates are elevated by two orders of magnitude, helicase activity is robust on circular templates, and affinity for DNA substrates is improved. The GINS proteins contribute to DNA substrate affinity and bind specifically to the MCM4 subunit. All pairwise associations among GINS, MCMs, and Cdc45 were detected, but tight association takes place only in the CMG. The onset of DNA replication and unwinding may thus occur through allosteric changes in MCM2-7 affected by the association of these ancillary factors.
authors.affiliation: Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Berkeley, Berkeley, CA 94720, USA.
authors.forename: Ivar
authors.initials: I
authors.lastname: Ilves
authors.forename: Tatjana
authors.initials: T
authors.lastname: Petojevic
authors.forename: James J
authors.initials: JJ
authors.lastname: Pesavento
authors.forename: Michael R
authors.initials: MR
authors.lastname: Botchan
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004261:DNA Replication; D029721:Drosophila Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D004331:Drosophila melanogaster / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D008954:Models, Biological; D008969:Molecular Sequence Data; D016415:Sequence Alignment
chemical_list: C547399:Cdc45 protein, Drosophila; D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D000255:Adenosine Triphosphate; D004247:DNA