Metastasis Suppressor NME1 Modulates Choice of Double-Strand Break Repair Pathways in Melanoma Cells by Enhancing Alternative NHEJ while Inhibiting NHEJ and HR

Abstract

Reduced NME1 expression in melanoma cell lines, mouse models of melanoma, and melanoma specimens in human patients is associated with increased metastatic activity. Herein, we investigate the role of NME1 in repair of double-stranded breaks (DSBs) and choice of double-strand break repair (DSBR) pathways in melanoma cells. Using chromatin immunoprecipitation, NME1 was shown to be recruited rapidly and directly to DSBs generated by the homing endonuclease I-PpoI. NME1 was recruited to DSBs within 30 min, in concert with recruitment of ataxia-telangiectasia mutated (ATM) protein, an early step in DSBR complex formation, as well as loss of histone 2B. NME1 was detected up to 5 kb from the break site after DSB induction, suggesting a role in extending chromatin reorganization away from the repair site. shRNA-mediated silencing of NME1 expression led to increases in the homologous recombination (HR) and non-homologous end-joining (NHEJ) pathways of double-strand break repair (DSBR), and reduction in the low fidelity, alternative-NHEJ (A-NHEJ) pathway. These findings suggest low expression of NME1 drives DSBR towards higher fidelity pathways, conferring enhanced genomic stability necessary for rapid and error-free proliferation in invasive and metastatic cells. The novel mechanism highlighted in the current study appears likely to impact metastatic potential and therapy-resistance in advanced melanoma and other cancers.

Alpha-synuclein regulates nucleolar DNA double-strand break repair in melanoma

“…Estimates suggest that up to 60% of all transcription within a normal mammalian cell occurs at rDNA 90 , and faithful ribosome biogenesis is even more important in malignant cells to sustain their increased levels of cell division and growth 91, 92 . In melanoma specifically, substantial evidence suggests that there is upregulation of DSB repair pathways to promote increased DSB repair capacity critical for survival 93, 94 . Evidence for this includes melanoma’s relative resistance to ionizing radiation 95, 96 and that DSB repair inhibitors are particularly effective in many treatment models 97, 98 .…”

The Complex Functions of the NME Family—A Matter of Location and Molecular Activity

“…NME1 and NME3 are also recruited to sites of DNA damage where they play a role in the repair of DNA single- and double strand breaks. Puts et al (University of Maryland, Baltimore, MD, USA [ 24 ]) describe the role of NME1 in the repair of DNA double-strand breaks, in particular the choice of the repair pathway. Nuclear NMEs can also interact with telomers, and Sharma et al (CSIR, New Delhi, India [ 25 ]) review the role of telomer-localized NMEs for regulating telomer-related factors.…”