WWOX, the common fragile site FRA16D gene product, regulates ATM activation and the DNA damage response

Abstract

Genomic instability is a hallmark of cancer. The WW domaincontaining oxidoreductase (WWOX) is a tumor suppressor spanning the common chromosomal fragile site FRA16D. Here, we report a direct role of WWOX in DNA damage response (DDR) and DNA repair. We show that Wwox deficiency results in reduced activation of the ataxia telangiectasia-mutated (ATM) checkpoint kinase, inefficient induction and maintenance of γ-H2AX foci, and impaired DNA repair. Mechanistically, we show that, upon DNA damage, WWOX accumulates in the cell nucleus, where it interacts with ATM and enhances its activation. Nuclear accumulation of WWOX is regulated by its K63-linked ubiquitination at lysine residue 274, which is mediated by the E3 ubiquitin ligase ITCH. These findings identify a novel role for the tumor suppressor WWOX and show that loss of WWOX expression may drive genomic instability and provide an advantage for clonal expansion of neoplastic cells.genomic instability | common fragile sites | WW domain-containing oxidoreductase | ataxia telangiectasia-mutated | ITCH G enomic instability is a common characteristic of human cancers. The DNA damage response (DDR) maintains the integrity of the genome in response to DNA damage. DDR is a complex signaling process that results in cell cycle arrest followed by either DNA repair or apoptosis if the DNA damage is too extensive to be repaired (1-3). Key mammalian damage response sensors are ataxia telangiectasia-mutated (ATM), ATM and Rad3-related, and DNA-dependent PKs (4, 5). Disruption of the DDR machinery in human cells leads to genomic instability and an increased risk of cancer progression (6, 7).The WW domain-containing oxidoreductase (WWOX) gene spans the common fragile site (CFS) FRA16D (8, 9). Genomic alterations affecting the WWOX locus have been reported in several types of cancer and include homozygous and hemizygous deletions (10-13). Ectopic expression of WWOX in WWOXnegative cancer cells attenuates cell growth and suppresses tumor growth in immunocompromised mice (10,11,14). Importantly, targeted ablation of Wwox in mice results in higher incidence of spontaneous lesions resembling osteosarcomas and lung and mammary tumors (14-16). These findings suggest WWOX as a tumor suppressor. The WWOX protein contains two Nterminal WW domains mediating WWOX interaction with PP(proline)x(amino acid)Y(tyrosine)-containing proteins (11, 17) and a central short-chain deyhdrogenase/reductase domain that has been proposed to function in steroidogenesis (18). Recent characterization of WWOX domains revealed that they interact, mainly through the WW1 domain, with multiprotein networks (3). The mechanism by which WWOX suppresses tumorigenicity is, however, not well-known.In vitro, CFSs are defined as gaps or breaks on metaphase chromosomes that occur in cells treated with inhibitors of DNA replication (19,20). In vivo, CFSs are preferential targets of replication stress in preneoplastic lesions (21), and emerging evidence suggests that they represent early warning sensors for DNA damage (22-24). ...

Sister chromatid telomere fusions, but not NHEJ-mediated inter-chromosomal telomere fusions, occur independently of DNA ligases 3 and 4

“…2G) and markedly higher than all other HCT116 lines. Since expression of the viral E6E7 proteins in MRC5 cells suppresses TP53 function (Shay et al 1993;Li et al 1998), these data reveal the importance of the TP53 checkpoint for exonucleolytic proof-reading (Akyüz et al 2002) and the suppression of DNA damage accumulation and NHEJ repair at telomeres (Abu-Odeh et al 2014), as well as the inhibition of cell division of genetically unstable cells (Bunz Telomere fusions were detected following Southern blotting using the 17p hybridization probe. Fusion frequency estimated empirically is recorded beneath the panels.…”

HYAL-2–WWOX–SMAD4 Signaling in Cell Death and Anticancer Response

“…Loss of WWOX gene expression can be due to hypermethylation of gene promoter (Iliopoulos et al, 2005; Chang et al, 2010; Gardenswartz and Aqeilan, 2014). When cytosolic WWOX protein relocates to the nucleus under stress conditions, WWOX is able to maintain genomic stability by controlling ATM activation and DNA damage response (Abu-Odeh et al, 2014; Abu-Remaileh et al, 2015). Most recently, WWOX-mediated suppression of cancer cell growth has been established in Drosophila (O'Keefe et al, 2015).…”

Recurrent alterations of the WW domain containing oxidoreductase gene spanning the common fragile site FRA16D in multiple myeloma and monoclonal gammopathy of undetermined significance

“…The instability of CFSs correlates with genomic instability in precancerous lesions (50) and the early stages of oncogenesis are associated with the DNA damage response (50,51). Genomic instability and abnormalities are hallmarks of MM, and aberrant DNA repair pathways are involved in disease onset and progression (52).…”

“…Genomic instability and abnormalities are hallmarks of MM, and aberrant DNA repair pathways are involved in disease onset and progression (52). WWOX deficiency reduces the levels of ATM serine/threonine kinase and impairs DNA repair, which may drive genomic instability (51). Therefore, WWOX alterations may also cause genomic instability.…”