Mutation Research 778 (2015) 71–79 Contents lists available at ScienceDirect Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis journal homepage: www.elsevier.com/locate/molmut Community address: www.elsevier.com/locate/mutres MKP1 phosphatase mediates G1-specific dephosphorylation of H3Serine10P in response to DNA damage Ajit K. Sharma, Shafqat A. Khan, Asmita Sharda, Divya V Reddy, Sanjay Gupta ∗ Epigenetics and Chromatin Biology Group, Gupta Lab, Cancer Research Institute, Advanced Centre for Treatment Research and Education in Cancer (ACTREC), Tata Memorial Centre, Kharghar, Navi Mumbai 410210 MH, India article info Article history: Received 7 April 2014 Received in revised form 25 May 2015 Accepted 1 June 2015 Available online 23 June 2015 Keywords: Cell cycle H3serine10 phosphorylation DNA damage response Kinases Phosphatases abstract Histone mark, H3S10 phosphorylation plays a dual role in a cell by maintaining relaxed chromatin for active transcription in interphase and condensed chromatin state in mitosis. The level of H3S10P has also been shown to alter on DNA damage; however, its cell cycle specific behavior and regulation during DNA damage response is largely unexplored. In the present study, we demonstrate G1 cell cycle phase specific reversible loss of H3S10P in response to IR-induced DNA damage is mediated by opposing activities of phosphatase, MKP1 and kinase, MSK1 of the MAP kinase pathway. We also show that the MKP1 recruits to the chromatin in response to DNA damage and correlates with the decrease of H3S10P, whereas MKP1 is released from chromatin during recovery phase of DDR. Furthermore, blocking of H3S10 dephospho- rylation by MKP1 inhibition impairs DNA repair process and results in poor survival of WRL68 cells. Collectively, our data proposes a pathway regulating G1 cell cycle phase specific reversible reduction of H3S10P on IR induced DNA damage and also raises the possibility of combinatorial modulation of H3S10P with specific inhibitors to target the cancer cells in G1-phase of cell cycle. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Previous studies in different models from yeast to human cells imply that chromatin structure serves as a barrier for repair at DNA damage sites. The complex array of histone modifications/ variants alter the overall charge and conformation of chromatin which helps in recruitment of factors at damage site to facilitate repair, and thus maintaining genomic integrity in response to DNA damaging agents [1,2]. Recent studies have unraveled the significant role of histone post-translational modifications (PTMs) in DNA damage response (DDR) [3]. The interplay between the DDR and chromatin dynamics has been proposed as a new model involving priming of chromatin for repair and restoration as a concerted process [4]. Histone mark, H3S10 phosphorylation alters throughout cell cycle and plays a dual role in different phases of cell cycle by main- taining relaxed chromatin for active transcription in interphase and condensed chromatin state in mitosis [5]. Recent literature suggests Abbreviations: DDR, DNA damage response; MSK1, Mitogen and stress-activated protein kinase-1; MKP1, Mitogen-activated protein kinase phosphatase-1; ATM, Ataxia telangiectasia mutated; VEGF, Vascular endothelial growth factor; S10P, ser- ine10 phosphorylation; IR, ionization radiation. ∗ Corresponding author. Tel.: +91 22 27405086; fax: +91 22 27405086. E-mail address: sgupta@actrec.gov.in (S. Gupta). that H3S10P is regulated by competing activities of different pro- tein kinases and phosphatases under different cell cycle phases and physiological conditions [6]. For example, aurora kinase mediates phosphorylation of H3S10 during the mitotic phase [7,8] whereas MSK1 and IKK- target H3S10 during interphase [9–11]. Among the phosphatases, MKP1 is shown to be overexpressed on irradiation both in cell culture and tumor tissues [12] and has been recently shown to dephosphorylate H3S10P in response to VEGF and throm- bin [13]. However, effector phosphatase and kinase which regulates dynamic level of H3S10P during DDR is not known. In the present study, we report G1 cell cycle phase specific reversible dynamics of H3S10P in response to IR induced DNA dam- age is regulated through downstream phosphatase, MKP1 and the kinase, MSK1 of MAP kinase pathway. We also demonstrate that MKP1 gets recruited to chromatin after DNA damage and released from chromatin during recovery phase, which closely correlates with reversible reduction of H3S10P during DDR. Furthermore, blocking the reduction of H3S10P by MKP1 inhibitor sanguinarine impairs DNA repair processes and results in poor survival of cells after IR induced DNA damage. Taken together, our results suggest a pathway which regulates dynamic alteration of H3S10P which facilitates efficient double strand DNA repair, and confers survival and growth advantage during IR induced DNA damage response. http://dx.doi.org/10.1016/j.mrfmmm.2015.06.001 0027-5107/© 2015 Elsevier B.V. All rights reserved.