The Metastasis Suppressor Nme1 Is Recruited To Dna Double Strand Breaks

NME1 is a potent suppressor of metastasis, and reduced expression has been associated with aggressive melanoma. The nucleoside diphosphate kinase and 3’-5’ exonuclease (3’-5’ EXO) activities of NME1 protein both contribute to its metastasis suppressor activity. 3’-5’ exonucleases are important for proofreading during DNA repair and synthesis, suggesting a potential role for NME1 in maintenance of genomic stability in melanoma. Although impairment of DNA repair activity has been implicated in melanoma risk, its contribution to melanoma initiation and progression is not well understood. We have shown previously that both enzymatic activities of NME1 are critical for repair of UV-induced DNA damage via nucleotide excision repair. In the current study, chromatin immunoprecipitation was used to demonstrate recruitment of NME1 to DNA double-strand breaks (DSBs), representing the first evidence of direct recruitment of NME1 to sites of DNA damage. Induction of DSBs with gamma irradiation (γ-IR) or bleomycin promoted rapid physical association of NME1 with γH2AX, ATM, NBS1 and RAD50. In addition, treatment of melanoma cells with γ-IR triggered a physical association of NME1 with XRCC4, an effector of the non-homologous end-joining (NHEJ) pathway. We are currently investigating whether knockout of NME1 induces a switch from NHEJ to the homologous recombination (HR) pathway, a slower but higher fidelity form of DSB repair, using plasmid repair assays. We are also using plasmid rescue to study the role of NME1 on the fidelity of NHEJ repair. Overall, our study indicates for the first time direct participation of NME1 in a molecular mechanism of DSB repair in both normal and transformed cells. In addition, these data suggest a novel mechanism of metastasis suppressor function for NME1, with loss of NME expression in tumor cells conferring genetic instability and enhanced metastatic potential. Citation Format: Gemma S. Puts, Stuart G. Jarrett, Devin Snyder, Richard Vincent, Ying Wang, Katie Leonard, Ben Portney, Feyruz Rassool, Michal Zalzman, David M. Kaetzel. The metastasis suppressor NME1 is recruited to DNA double strand breaks [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4846. doi:10.1158/1538-7445.AM2017-4846