title: BRCA1 is required for hMLH1 stabilization following doxorubicin-induced DNA damage.
abstract: Human DNA mismatch repair (MMR) is involved in the removal of DNA base mismatches that arise either during DNA replication or are caused by DNA damage. In this study, we show that the activation of the MMR component hMLH1 in response to doxorubicin (DOX) treatment requires the presence of BRCA1 and that this phenomenon is mediated by an ATM/ATR dependent phosphorylation of the hMLH1 Ser-406 residue. BRCA1 is an oncosuppressor protein with a central role in the DNA damage response and it is a critical component of the ATM/ATR mediated checkpoint signaling. Starting from a previous finding in which we demonstrated that hMLH1 is able to bind to BRCA1, in this study we asked whether BRCA1 might be the bridge for ATM/ATR dependent phosphorylation of the hMLH1 molecular partner. We found that: (i) the negative modulation of BRCA1 expression is able to produce a remarkable reversal of hMLH1 stabilization, (ii) BRCA1 is required for post-translational modification produced by DOX treatment on hMLH1 which is, in turn, attributed to the ATM/ATR activity, (iii) the serine 406 phosphorylatable residue is critical for hMLH1 activation by ATM/ATR via BRCA1. Taken together, our data lend support to the hypothesis suggesting an important role of this oncosuppressor as a scaffold or bridging protein in DNA-damage response signaling via downstream phosphorylation of the ATM/ATR substrate hMLH1.
authors.affiliation: Department of Experimental and Clinical Medicine, Magna Græcia University of Catanzaro, Salvatore Venuta Campus, Viale Europa, 88100 Catanzaro, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Romeo
authors.forename: Lucia
authors.initials: L
authors.lastname: Falbo
authors.forename: Maddalena
authors.initials: M
authors.lastname: Di Sanzo
authors.forename: Roberta
authors.initials: R
authors.lastname: Misaggi
authors.forename: Maria C
authors.initials: MC
authors.lastname: Faniello
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Viglietto
authors.forename: Giovanni
authors.initials: G
authors.lastname: Cuda
authors.forename: Francesco
authors.initials: F
authors.lastname: Costanzo
authors.forename: Barbara
authors.initials: B
authors.lastname: Quaresima
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D019313:BRCA1 Protein / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D004249:DNA Damage; D004317:Doxorubicin / Q000494:pharmacology*; D006801:Humans; D000070957:MutL Protein Homolog 1; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D012694:Serine / Q000235:genetics; D015398:Signal Transduction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000903:Antibiotics, Antineoplastic; D019313:BRCA1 Protein; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D012694:Serine; D004317:Doxorubicin; D004247:DNA; D000070957:MutL Protein Homolog 1