Cell-type specific role of the RNA-binding protein, NONO, in the DNA double-strand break response in the mouse testes

• Authors: Shuyi Li, Emory University; Feng-jue Shu, Emory University; Zhentian Li, Emory University; Lahcen Jaafar, Emory University; Shourong Zhao, Columbus Pathology; William Dynan, Emory University
• Journal Title: DNA Repair
• Volume: Volume 51
• Publisher: Elsevier | 2017-03-01, Pages 70-78
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1016/j.dnarep.2017.02.002
• Subjects: Biology, Cell; Health Sciences, Oncology; Biology, Genetics
• Keywords: Science & Technology; Life Sciences & Biomedicine; Genetics & Heredity; Toxicology; NONO; Double-strand break repair; NHEJ; Ionizing radiation; Knockout mouse; Testes; SPLICING-FACTOR; DAMAGE RESPONSE; GENE-REGULATION; PSF; REPAIR; SPERMATOGENESIS; TRANSCRIPTION; CONNEXIN-43; P54(NRB); COMPLEX

Abstract

The tandem RNA recognition motif protein, NONO, was previously identified as a candidate DNA double-strand break (DSB) repair factor in a biochemical screen for proteins with end-joining stimulatory activity. Subsequent work showed that NONO and its binding partner, SFPQ, have many of the properties expected for bona fide repair factors in cell-based assays. Their contribution to the DNA damage response in intact tissue in vivo has not, however, been demonstrated. Here we compare DNA damage sensitivity in the testes of wild-type mice versus mice bearing a null allele of the NONO homologue (Nono gt ). In wild-type mice, NONO protein was present in Sertoli, peritubular myoid, and interstitial cells, with an increase in expression following induction of DNA damage. As expected for the product of an X-linked gene, NONO was not detected in germ cells. The Nono gt/0 mice had at most a mild testis developmental phenotype in the absence of genotoxic stress. However, following irradiation at sublethal, 2–4 Gy doses, Nono gt/0 mice displayed a number of indicators of radiosensitivity as compared to their wild-type counterparts. These included higher levels of persistent DSB repair foci, increased numbers of apoptotic cells in the seminiferous tubules, and partial degeneration of the blood-testis barrier. There was also an almost complete loss of germ cells at later times following irradiation, evidently arising as an indirect effect reflecting loss of stromal support. Results demonstrate a role for NONO protein in protection against direct and indirect biological effects of ionizing radiation in the whole animal.