The NEIL1 G83D germline DNA glycosylase variant induces genomic instability and cellular transformation
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Heather A. Galick1, Carolyn G. Marsden1, Scott Kathe1, Julie A. Dragon1, Lindsay Volk3, Antonia A. Nemec4, Susan S. Wallace1, Aishwarya Prakash5, Sylvie Doublié1 and Joann B. Sweasy1,2
1Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, University of Vermont, Burlington, VT, 05405, USA
2Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT, 06510, USA
3Present address: University of New Mexico, Health Sciences Center, Albuquerque, NM, 87131, USA
4Department of Biomedical Sciences, Florida State University, Tallahassee, FL, 32306, USA
5Present address: University of South Alabama, Mitchell Cancer Institute, Mobile, AL, 36604, USA
Joann B. Sweasy, email: [email protected]
Keywords base excision repair, genomic instability, replication fork collapse, DNA glycosylase, mutagenesis
Received: April 13, 2017 Accepted: August 04, 2017 Published: September 08, 2017
Base excision repair (BER) is a key genome maintenance pathway. The NEIL1 DNA glycosylase recognizes oxidized bases, and likely removes damage in advance of the replication fork. The rs5745906 SNP of the NEIL1 gene is a rare human germline variant that encodes the NEIL1 G83D protein, which is devoid of DNA glycosylase activity. Here we show that expression of G83D NEIL1 in MCF10A immortalized but non-transformed mammary epithelial cells leads to replication fork stress. Upon treatment with hydrogen peroxide, we observe increased levels of stalled replication forks in cells expressing G83D NEIL1 versus cells expressing the wild-type (WT) protein. Double-strand breaks (DSBs) arise in G83D-expressing cells during the S and G2/M phases of the cell cycle. Interestingly, these breaks result in genomic instability in the form of high levels of chromosomal aberrations and micronuclei. Cells expressing G83D also grow in an anchorage independent manner, suggesting that the genomic instability results in a carcinogenic phenotype. Our results are consistent with the idea that an inability to remove oxidative damage in an efficient manner at the replication fork leads to genomic instability and mutagenesis. We suggest that individuals who harbor the G83D NEIL1 variant face an increased risk for human cancer.
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