title: Histone deacetylase inhibitors decrease NHEJ both by acetylation of repair factors and trapping of PARP1 at DNA double-strand breaks in chromatin.
abstract: Histone deacetylase inhibitors (HDACi) induce acetylation of histone and non-histone proteins, and modulate the acetylation of proteins involved in DNA double-strand break (DSB) repair. Non-homologous end-joining (NHEJ) is one of the main pathways for repairing DSBs. Decreased NHEJ activity has been reported with HDACi treatment. However, mechanisms through which these effects are regulated in the context of chromatin are unclear. We show that pan-HDACi, trichostatin A (TSA), causes differential acetylation of DNA repair factors Ku70/Ku80 and poly ADP-ribose polymerase-1 (PARP1), and impairs NHEJ. Repair effects are reversed by treatments with p300/CBP inhibitor C646, with significantly decreased acetylation of PARP1. In keeping with these findings, TSA treatment significantly increases PARP1 binding to DSBs in chromatin. Notably, AML patients treated with HDACi entinostat (MS275) in vivo also show increased formation of poly ADP-ribose (PAR) that co-localizes with DSBs. Further, we demonstrate that PARP1 bound to chromatin increases with duration of TSA exposure, resembling PARP "trapping". Knockdown of PARP1 inhibits trapping and mitigates HDACi effects on NHEJ. Finally, combination of HDACi with potent PARP inhibitor talazoparib (BMN673) shows a dose-dependent increase in PARP "trapping", which correlates with increased apoptosis. These results provide a mechanism through which HDACi inhibits deacetylation and increases binding of PARP1 to DSBs, leading to decreased NHEJ and cytotoxicity of leukemia cells.
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD 21201, United States.
authors.forename: Carine
authors.initials: C
authors.lastname: Robert
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD 21201, United States.
authors.forename: Pratik K
authors.initials: PK
authors.lastname: Nagaria
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD 21201, United States.
authors.forename: Nisha
authors.initials: N
authors.lastname: Pawar
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD 21201, United States.
authors.forename: Adeoluwa
authors.initials: A
authors.lastname: Adewuyi
authors.affiliation: The Sidney Kimmel Comprehensive Cancer Center, School of Medicine, Johns Hopkins University, United States.
authors.forename: Ivana
authors.initials: I
authors.lastname: Gojo
authors.affiliation: Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States.
authors.forename: David J
authors.initials: DJ
authors.lastname: Meyers
authors.affiliation: Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Cole
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD 21201, United States. Electronic address: frassool@som.umaryland.edu.
authors.forename: Feyruz V
authors.initials: FV
authors.lastname: Rassool
mesh_terms: D000107:Acetylation; D001549:Benzamides / Q000494:pharmacology; D002843:Chromatin / Q000378:metabolism*; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects*; D059766:DNA End-Joining Repair / Q000187:drug effects*; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D000072200:Ku Autoantigen / Q000378:metabolism*; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy; D000071137:Poly (ADP-Ribose) Polymerase-1 / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D001549:Benzamides; D002843:Chromatin; D056572:Histone Deacetylase Inhibitors; D011725:Pyridines; C118739:entinostat; D000071137:Poly (ADP-Ribose) Polymerase-1; D000072200:Ku Autoantigen
keywords: DSB repair; HDAC; NHEJ; PARP1