Double-strand break repair deficiency in NONO knockout murine embryonic fibroblasts and compensation by spontaneous upregulation of the PSPC1 paralog

• Type of Material: Article
• Authors: Shuyi Li, Emory University; Zhentian Li, affiliation; Feng-Jue Shu, Georgia Regents University; Hairong Xiong, Georgia Regents University; Andrew C. Phillips, Georgia Regents University; William Dynan, Emory University
• Language: English
• Date: 2014-01-01
• Publisher: Oxford University Press
• Publication Version: Final Published Version
• Copyright Statement: © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.
• License: Creative Commons Attribution-NonCommercial 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1093/nar/gku650
• Title of Journal or Parent Work: Nucleic Acids Research
• ISSN: 0305-1048
• Volume: 42
• Issue: 15
• Start Page: 9771
• End Page: 9780
• Grant/Funding Information: Funding for open access charge: National Institutes of Health [2 R01 CA98239].; W. Dynan also received support as an Eminent Scholar of the Georgia Research Alliance.; National Institutes of Health [2 R01 CA98239].
• Keywords: Life Sciences & Biomedicine; ANDROGEN RECEPTOR; DNA-DAMAGE RESPONSE; GENE-EXPRESSION; RNA-BINDING PROTEINS; LONG NONCODING RNA; CELL-PROLIFERATION; GENOME INSTABILITY; TRANSCRIPTION TERMINATION; SPLICING-FACTOR; Science & Technology; Biochemistry & Molecular Biology; NUCLEAR RETENTION
• Research Categories: Chemistry, Biochemistry; Biology, Genetics

Abstract

NONO, SFPQ and PSPC1 make up a family of proteins with diverse roles in transcription, RNA processing and DNA double-strand break (DSB) repair. To understand long-term effects of loss of NONO, we characterized murine embryonic fibroblasts (MEFs) from knockout mice. In the absence of genotoxic stress, wild-type and mutant MEFs showed similar growth rates and cell cycle distributions, and the mutants were only mildly radiosensitive. Further investigation showed that NONO deficiency led to upregulation of PSPC1, which replaced NONO in a stable complex with SFPQ. Knockdown of PSPC1 in a NONO-deficient background led to severe radiosensitivity and delayed resolution of DSB repair foci. The DNA-dependent protein kinase (DNA-PK) inhibitor, NU7741, sensitized wild-type and singly deficient MEFs, but had no additional effect on doubly deficient cells, suggesting that NONO/PSPC1 and DNA-PK function in the same pathway. We tested whether NONO and PSPC1 might also affect repair indirectly by influencing mRNA levels for other DSB repair genes. Of 12 genes tested, none were downregulated, and several were upregulated. Thus, NONO or related proteins are critical for DSB repair, NONO and PSPC1 are functional homologs with partially interchangeable functions and a compensatory response involving PSPC1 blunts the effect of NONO deficiency.