title: Checkpoint kinase 2 (Chk2) inhibits the activity of the Cdc45/MCM2-7/GINS (CMG) replicative helicase complex.
abstract: The replication of eukaryote chromosomes slows down when DNA is damaged and the proteins that work at the fork (the replisome) are known targets for the signaling pathways that mediate such responses critical for accurate genomic inheritance. However, the molecular mechanisms and details of how this response is mediated are poorly understood. In this report we show that the activity of replisome helicase, the Cdc45/MCM2-7/GINS (CMG) complex, can be inhibited by protein phosphorylation. Recombinant Drosophila melanogaster CMG can be stimulated by treatment with phosphatase whereas Chk2 but not Chk1 interferes with the helicase activity in vitro. The targets for Chk2 phosphorylation have been identified and reside in MCM subunits 3 and 4 and in the GINS protein Psf2. Interference requires a combination of modifications and we suggest that the formation of negative charges might create a surface on the helicase to allosterically affect its function. The treatment of developing fly embryos with ionizing radiation leads to hyperphosphorylation of Psf2 subunit in the active helicase complex. Taken together these data suggest that the direct modification of the CMG helicase by Chk2 is an important nexus for response to DNA damage.
authors.affiliation: Division of Biochemistry and Molecular Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
authors.forename: Ivar
authors.initials: I
authors.lastname: Ilves
authors.forename: Nele
authors.initials: N
authors.lastname: Tamberg
authors.forename: Michael R
authors.initials: MR
authors.lastname: Botchan
mesh_terms: D000818:Animals; D064447:Checkpoint Kinase 2; D004265:DNA Helicases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004261:DNA Replication / Q000528:radiation effects; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000196:embryology / Q000201:enzymology* / Q000528:radiation effects; D004625:Embryo, Nonmammalian / Q000201:enzymology / Q000528:radiation effects; D046912:Multiprotein Complexes / Q000378:metabolism*; D010766:Phosphorylation / Q000528:radiation effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D011839:Radiation, Ionizing
chemical_list: D029721:Drosophila Proteins; D046912:Multiprotein Complexes; D021122:Protein Subunits; D064447:Checkpoint Kinase 2; D017346:Protein Serine-Threonine Kinases; D004265:DNA Helicases