title: Characterization of the role of a trimeric protein phosphatase complex in recovery from cisplatin-induced versus noncrosslinking DNA damage.
abstract: Cisplatin (cis-diamminedichloroplatinum) and related chemotherapeutic DNA-crosslinking agents are widely used to treat human cancers. Saccharomyces cerevisiae with separate deletions of the genes encoding the trimeric protein serine/threonine phosphatase (Pph)3p-platinum sensitivity (Psy)4p-Psy2p complex, are more sensitive than the isogenic wild-type (WT) strain to cisplatin. We show here that cisplatin causes an enhanced intra-S-phase cell cycle delay in these three deletion mutants. The C-terminal tail of histone 2AX (H2AX) is hyperphosphorylated in the same mutants, and Pph3p is found to interact with phosphorylated H2AX (gammaH2AX). After cisplatin treatment is terminated, pph3Delta, psy4Delta and psy2Delta mutants are delayed as compared with the WT strain in the dephosphorylation of Rad53p. In contrast, only pph3Delta and psy2Delta cells are more sensitive than WT cells to methylmethanesulfonate, a noncrosslinking DNA-alkylating agent that is known to cause a Rad53p-dependent intra-S-phase cell cycle delay. Dephosphorylation of Rad53p and the recovery of chromosome replication are delayed in the same mutants, but not in psy4Delta cells. By comparison with their mammalian orthologues, the regulatory subunit Psy4p is likely to inhibit Pph3p catalytic activity. The presence of a weak but active Pph3p-Psy2p complex may allow psy4Delta cells to escape from the Rad53p-mediated cell cycle arrest. Overall, our data suggest that the trimeric Pph3p-Psy4p-Psy2p complex may dephosphorylate both gammaH2AX and Rad53p, the differences lying in the more stable interaction of the Pph3 phosphatase with gammaH2AX as opposed to a transient interaction with Rad53p.
authors.affiliation: Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, UK.
authors.forename: Cristina
authors.initials: C
authors.lastname: Vázquez-Martin
authors.forename: John
authors.initials: J
authors.lastname: Rouse
authors.forename: Patricia T W
authors.initials: PT
authors.lastname: Cohen
mesh_terms: D000477:Alkylating Agents / Q000633:toxicity; D000970:Antineoplastic Agents / Q000633:toxicity*; D002453:Cell Cycle / Q000187:drug effects; D015825:Chromosomes, Fungal / Q000378:metabolism; D002945:Cisplatin / Q000633:toxicity*; D003432:Cross-Linking Reagents / Q000633:toxicity*; D004249:DNA Damage; D004261:DNA Replication; D017353:Gene Deletion; D006657:Histones / Q000378:metabolism; D008741:Methyl Methanesulfonate / Q000633:toxicity; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000502:physiology*; D021122:Protein Subunits / Q000235:genetics / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*
chemical_list: D000477:Alkylating Agents; D000970:Antineoplastic Agents; D003432:Cross-Linking Reagents; D006657:Histones; D009687:Nuclear Proteins; D021122:Protein Subunits; C494616:Psy2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D008741:Methyl Methanesulfonate; C531122:Psy4 protein, S cerevisiae; C502440:PPH3 protein, S cerevisiae; D010749:Phosphoprotein Phosphatases; D002945:Cisplatin