title: Kdm4b histone demethylase is a DNA damage response protein and confers a survival advantage following γ-irradiation.
abstract: DNA damage evokes a complex and highly coordinated DNA damage response (DDR) that is integral to the suppression of genomic instability. Double-strand breaks (DSBs) are considered the most deleterious form damage. Evidence suggests that trimethylation of histone H3 lysine 9 (H3K9me3) presents a barrier to DSB repair. Also, global levels of histone methylation are clinically predictive for several tumor types. Therefore, demethylation of H3K9 may be an important step in the repair of DSBs. The KDM4 subfamily of demethylases removes H3K9 tri- and dimethylation and contributes to the regulation of cellular differentiation and proliferation; mutation or aberrant expression of KDM4 proteins has been identified in several human tumors. We hypothesize that members of the KDM4 subfamily may be components of the DDR. We found that Kdm4b-enhanced GFP (EGFP) and KDM4D-EGFP were recruited rapidly to DNA damage induced by laser micro-irradiation. Focusing on the clinically relevant Kdm4b, we found that recruitment was dependent on poly(ADP-ribose) polymerase 1 activity as well as Kdm4b demethylase activity. The Kdm4 proteins did not measurably accumulate at γ-irradiation-induced γH2AX foci. Nevertheless, increased levels of Kdm4b were associated with decreased numbers of γH2AX foci 6 h after irradiation as well as increased cell survival. Finally, we found that levels of H3K9me2 and H3K9me3 were decreased at early time points after 2 gray of γ-irradiation. Taken together, these data demonstrate that Kdm4b is a DDR protein and that overexpression of Kdm4b may contribute to the failure of anti-cancer therapy that relies on the induction of DNA damage.
authors.affiliation: From the Cross Cancer Institute and the Department of Experimental Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 1Z2, Canada.
authors.forename: Leah C
authors.initials: LC
authors.lastname: Young
authors.affiliation: From the Cross Cancer Institute and the Department of Experimental Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 1Z2, Canada.
authors.forename: Darin W
authors.initials: DW
authors.lastname: McDonald
authors.affiliation: From the Cross Cancer Institute and the Department of Experimental Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 1Z2, Canada. Electronic address: mhendzel@ualberta.ca.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hendzel
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair / Q000528:radiation effects; D051747:DNA-Activated Protein Kinase / Q000378:metabolism; D036681:Fluorescence Recovery After Photobleaching; D005720:Gamma Rays; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D056484:Jumonji Domain-Containing Histone Demethylases / Q000378:metabolism*; D007834:Lasers; D008239:Lysine / Q000378:metabolism; D008745:Methylation / Q000528:radiation effects; D051379:Mice; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D021381:Protein Transport / Q000528:radiation effects; D011993:Recombinant Fusion Proteins / Q000378:metabolism
chemical_list: C468783:H2AX protein, human; D006657:Histones; D011993:Recombinant Fusion Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D056484:Jumonji Domain-Containing Histone Demethylases; D011065:Poly(ADP-ribose) Polymerases; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase; D008239:Lysine
keywords: Chromatin Regulation; Chromatin Remodeling; Chromatin Structure; DNA Damage Response; DNA Repair; Heterochromatin; Histone Methylation