Dewan A, Xing M, Lundbæk MB, Gago‐Fuentes R, Beck C, Aas PA, Liabakk N, Sæterstad S, Chau KTP, Kavli BM, Oksenych V. Robust DNA repair in PAXX-deficient mammalian cells.
FEBS Open Bio 2018;
8:442-448. [PMID:
29511621 PMCID:
PMC5832976 DOI:
10.1002/2211-5463.12380]
[Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Revised: 12/19/2017] [Accepted: 01/04/2018] [Indexed: 12/02/2022] Open
Abstract
To ensure genome stability, mammalian cells employ several DNA repair pathways. Nonhomologous DNA end joining (NHEJ) is the DNA repair process that fixes double-strand breaks throughout the cell cycle. NHEJ is involved in the development of B and T lymphocytes through its function in V(D)J recombination and class switch recombination (CSR). NHEJ consists of several core and accessory factors, including Ku70, Ku80, XRCC4, DNA ligase 4, DNA-PKcs, Artemis, and XLF. Paralog of XRCC4 and XLF (PAXX) is the recently described accessory NHEJ factor that structurally resembles XRCC4 and XLF and interacts with Ku70/Ku80. To determine the physiological role of PAXX in mammalian cells, we purchased and characterized a set of custom-generated and commercially available NHEJ-deficient human haploid HAP1 cells, PAXXΔ, XRCC4Δ , and XLFΔ . In our studies, HAP1 PAXXΔ cells demonstrated modest sensitivity to DNA damage, which was comparable to wild-type controls. By contrast, XRCC4Δ and XLFΔ HAP1 cells possessed significant DNA repair defects measured as sensitivity to double-strand break inducing agents and chromosomal breaks. To investigate the role of PAXX in CSR, we generated and characterized Paxx-/- and Aid-/- murine lymphoid CH12F3 cells. CSR to IgA was nearly at wild-type levels in the Paxx-/- cells and completely ablated in the absence of activation-induced cytidine deaminase (AID). In addition, Paxx-/- CH12F3 cells were hypersensitive to zeocin when compared to wild-type controls. We concluded that Paxx-deficient mammalian cells maintain robust NHEJ and CSR.
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