title: MAD2 interacts with DNA repair proteins and negatively regulates DNA damage repair.
abstract: MAD2 (mitotic arrest deficient 2) is a key regulator of mitosis. Recently, it had been suggested that MAD2-induced mitotic arrest mediates DNA damage response and that upregulation of MAD2 confers sensitivity to DNA-damaging anticancer drug-induced apoptosis. In this study, we report a potential novel role of MAD2 in mediating DNA nucleotide excision repair through physical interactions with two DNA repair proteins, XPD (xeroderma pigmentosum complementation group D) and ERCC1. First, overexpression of MAD2 resulted in decreased nuclear accumulation of XPD, a crucial step in the initiation of DNA repair. Second, immunoprecipitation experiments showed that MAD2 was able to bind to XPD, which led to competitive suppression of binding activity between XPD and XPA, resulting in the prevention of physical interactions between DNA repair proteins. Third, unlike its role in mitosis, the N-terminus domain seemed to be more important in the binding activity between MAD2 and XPD. Fourth, phosphorylation of H2AX, a process that is important for recruitment of DNA repair factors to DNA double-strand breaks, was suppressed in MAD2-overexpressing cells in response to DNA damage. These results suggest a negative role of MAD2 in DNA damage response, which may be accounted for its previously reported role in promoting sensitivity to DNA-damaging agents in cancer cells. However, the interaction between MAD2 and ERCC1 did not show any effect on the binding activity between ERCC1 and XPA in the presence or absence of DNA damage. Our results suggest a novel function of MAD2 by interfering with DNA repair proteins.
authors.affiliation: Department of Anatomy, Cancer Biology Group, Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong, SAR, China.
authors.forename: Maggie K L
authors.initials: MK
authors.lastname: Fung
authors.forename: Hui-Ying
authors.initials: HY
authors.lastname: Han
authors.forename: Steve C L
authors.initials: SC
authors.lastname: Leung
authors.forename: Hiu Wing
authors.initials: HW
authors.lastname: Cheung
authors.forename: Annie L M
authors.initials: AL
authors.lastname: Cheung
authors.forename: Yong-Chuan
authors.initials: YC
authors.lastname: Wong
authors.forename: Ming-Tat
authors.initials: MT
authors.lastname: Ling
authors.forename: Xianghong
authors.initials: X
authors.lastname: Wang
mesh_terms: D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002945:Cisplatin / Q000494:pharmacology; D004247:DNA / Q000235:genetics* / Q000378:metabolism*; D004249:DNA Damage / Q000235:genetics*; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006657:Histones / Q000378:metabolism; D006801:Humans; D064246:Mad2 Proteins; D011485:Protein Binding; D051135:Rad51 Recombinase / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D051759:Xeroderma Pigmentosum Group D Protein / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D006657:Histones; C577697:MAD2L1 protein, human; D064246:Mad2 Proteins; D012097:Repressor Proteins; D004247:DNA; D051135:Rad51 Recombinase; D051759:Xeroderma Pigmentosum Group D Protein; D002945:Cisplatin