title: H2AX phosphorylation after UV irradiation is triggered by DNA repair intermediates and is mediated by the ATR kinase.
abstract: It has been suggested that phosphorylation of the histone variant H2AX after ultraviolet light (UV) irradiation is triggered by DNA double-strand breaks induced as replication forks collide with UV-induced bulky lesions. More recently, it has been shown that UV-induced H2AX phosphorylation can also occur outside of S-phase, but the mechanism for this replication-independent induction is not well understood. In this study, we show that H2AX phosphorylation after UV irradiation is triggered by DNA repair intermediates and is induced in all phases of the cell cycle. Accumulation of DNA repair intermediates by inhibition of DNA repair synthesis resulted in a marked increase of H2AX phosphorylation in repair proficient but not repair-deficient xeroderma pigmentosum-A cells. Using chemical inhibitors of the PI(3)-like kinase family of protein kinases as well as ataxia telangiectasia mutated and Rad-3 related (ATR)-deficient Seckel syndrome cells and ataxia telangiectasia mutated-deficient ataxia telangiectasia cells, we show that the H2AX phosphorylation induced by accumulation of repair intermediates is mediated primarily by the ATR kinase. We suggest a model for UV light-induced phosphorylation of H2AX where in addition to replication blockage, DNA repair intermediates trigger H2AX phosphorylation via the ATR kinase.
authors.affiliation: Department of Radiation Oncology, Division of Radiation and Cancer Biology, University of Michigan Comprehensive Cancer Center, Ann Arbor, MI 48109-2200, USA.
authors.forename: Sheela
authors.initials: S
authors.lastname: Hanasoge
authors.forename: Mats
authors.initials: M
authors.lastname: Ljungman
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D015153:Blotting, Western; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism*; D004260:DNA Repair; D004307:Dose-Response Relationship, Radiation; D005434:Flow Cytometry; D006657:Histones / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D018797:Cell Cycle Proteins; C468783:H2AX protein, human; D006657:Histones; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases