Browsing by Author "Park, Jung-Young"

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    BREAST CANCER-ASSOCIATED MISSENSE MUTANTS OF THE PALB2 WD40 DOMAIN, WHICH DIRECTLY BINDS RAD51C, RAD51 AND BRCA2, DISRUPT DNA REPAIR
    (Nature Publishing Group, 2014-10-02) Park, Jung-Young; Singh, Thiyam R.; Nassar, Nicolas; Zhang, Fan; Freund, Marcel; Hanenberg, Helmut; Meetei, Amom Ruhikanta; Andreassen, Paul R.; Department of Pediatrics, IU School of Medicine
    Heterozygous carriers of germ-line mutations in the BRCA2/FANCD1, PALB2/FANCN, and RAD51C/FANCO DNA repair genes have an increased life-time risk to develop breast, ovarian and other cancers; bi-allelic mutations in these genes clinically manifest as Fanconi anemia (FA). Here, we demonstrate that RAD51C is part of a novel protein complex that contains PALB2 and BRCA2. Further, the PALB2 WD40 domain can directly and independently bind RAD51C and BRCA2. To understand the role of these homologous recombination (HR) proteins in DNA repair, we functionally characterize effects of missense mutations of the PALB2 WD40 domain that have been reported in breast cancer patients. In contrast to large truncations of PALB2, which display a complete loss of interaction, the L939W, T1030I, and L1143P missense mutants/variants of PALB2 WD40 domain are associated with altered direct binding patterns to the RAD51C, RAD51 and BRCA2 HR proteins in biochemical assays. Further, the T1030I missense mutant is unstable, while the L939W and L1143P proteins are stable but partially disrupt the PALB2-RAD51C-BRCA2 complex in cells. Functionally, the L939W and L1143P mutants display a decreased capacity for DNA double-strand break-induced HR and an increased cellular sensitivity to ionizing radiation. As further evidence for the functional importance of the HR complex, RAD51C mutants that are associated with cancer susceptibility and FA also display decreased complex formation with PALB2. Together, our results suggest that three different cancer susceptibility and FA proteins function in a DNA repair pathway based upon the PALB2 WD40 domain binding to RAD51C and BRCA2.
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    Complementation of hypersensitivity to DNA interstrand crosslinking agents demonstrates that XRCC2 is a Fanconi anaemia gene
    (BMJ Journals, 2016-10) Park, Jung-Young; Virts, Elizabeth L.; Jankowska, Anna; Wiek, Constanze; Othman, Mohamed; Chakraborty, Sujata C.; Vance, Gail H.; Alkuraya, Fowzan S.; Hanenberg, Helmut; Andreassen, Paul R.; Medical and Molecular Genetics, School of Medicine
    Background Fanconi anemia (FA) is a heterogeneous inherited disorder clinically characterized by progressive bone marrow failure, congenital anomalies, and a predisposition to malignancies. Objective Determine, based on correction of cellular phenotypes, whether XRCC2 is a FA gene. Methods Cells (900677) from a previously identified patient with biallelic mutation of XRCC2, among other mutations, were genetically complemented with wild-type XRCC2. Results Wild-type XRCC2 corrects each of three phenotypes characteristic of FA cells, all related to the repair of DNA interstrand crosslinks, including increased sensitivity to mitomycin C (MMC), chromosome breakage, and G2-M accumulation in the cell cycle. Further, the p.R215X mutant of XRCC2, which is harbored by the patient, is unstable. This provides an explanation for the pathogenesis of this mutant, as does the fact that 900677 cells have reduced levels of other proteins in the XRCC2-RAD51B-C-D complex. Also, FANCD2 monoubiquitination and foci formation, but not assembly of RAD51 foci, are normal in 900677 cells. Thus, XRCC2 acts late in the FA-BRCA pathway as also suggested by hypersensitivity of 900677 cells to ionizing radiation. These cells also share milder sensitivities toward olaparib and formaldehyde with certain other FA cells. Conclusions XRCC2/FANCU is a FA gene, as is another RAD51 paralog gene, RAD51C/FANCO. Notably, similar to a subset of FA genes that act downstream of FANCD2, biallelic mutation of XRCC2/FANCU has not been associated with bone marrow failure. Taken together, our results yield important insights into phenotypes related to FA and its genetic origins.