Poor recognition of O6-isopropyl dG by MGMT triggers double strand break-mediated cell death and micronucleus induction in FANC-deficient cells

摘要: // Kiyohiro Hashimoto 1, 2 , Vyom Sharma 1 Hiroyuki Sasanuma 3 Xu Tian Minoru Takata 4 Shunichi Takeda James A. Swenberg Jun Nakamura Department of Environmental Sciences and Engineering, University North Carolina at Chapel Hill, NC 27516, USA Drug Safety Research Laboratories, Pharmaceutical Division, Company Limited, Fujisawa, Kanagawa 251-8555, Japan Radiation Genetics, Kyoto University, Graduate School Medicine, Yoshida Konoe, Sakyo-ku, 606-8501, Laboratory DNA Damage Signaling, Late Effects Studies, Biology Center, Correspondence to: Nakamura, email: ynakamur@email.unc.edu Keywords: isopropyl methanesulfonate, alkylation, DT40, FANC, micronucleus Received: March 10, 2016     Accepted: July 18, Published: 29, 2016 ABSTRACT Isopropyl methanesulfonate (IPMS) is the most potent genotoxic compound among methanesulfonic acid esters. The potential alkyl sulfonate esters believed to be due their alkylating ability O6 position guanine. Understanding primary repair pathway activated in response IPMS-induced damage important profile IPMS. In present study, both chicken DT40 human TK6 cell-based (DDR) assays revealed that dysfunction FANC resulted higher sensitivity IPMS compared EMS or MMS. O6-alkyl dG primarily repaired by methyl guanine methyltransferase (MGMT), while less likely a substrate for MGMT. Comparison cytotoxic its isomer n-propyl (nPMS) moiety avoids recognition MGMT leads cytotoxicity. Next, (MN) assay showed deficiency increases cells MN induction Pretreatment with O6-benzyl (OBG), an inhibitor MGMT, increased frequency treated nPMS, but not Lastly, induced more double strand breaks -deficient wild-type time-dependent manner. All together, these results suggest IPMS-derived O6-isopropyl escapes unrepaired breaks, resulting induction. therefore, plays pivotal role preventing cell death caused