title: MAGE-C2 promotes growth and tumorigenicity of melanoma cells, phosphorylation of KAP1, and DNA damage repair.
abstract: Melanoma-associated antigen-encoding (MAGE) genes are expressed in melanoma and other cancers but not in normal somatic cells. MAGE expression is associated with aggressive tumor growth, poor clinical outcome, and resistance to chemotherapy, but the mechanisms have not been completely elucidated. In this study, we show that downregulation of MAGE-C2 in A375 melanoma cells and low-passage cultures from human metastatic melanomas (MRA cells) results in increased apoptosis and decreased growth of tumor xenografts in athymic nude mice. Previously, we showed that MAGE-C2 binds KAP1, a scaffolding protein that regulates DNA repair. Phosphorylation of KAP1-Serine 824 (Ser824) by ataxia-telangiectasia-mutated (ATM) kinase is necessary for repair of DNA double-strand breaks (DSBs); now we show that MAGE-C2 knockdown reduces, whereas MAGE-C2 overexpression increases, ATM kinase-dependent phosphorylation of KAP1-Ser824. We demonstrate that MAGE-C2 increases co-precipitation of KAP1 with ATM and that binding of MAGE-C2 to KAP1 is necessary for increased KAP1-Ser824 phosphorylation. Furthermore, ectopic expression of MAGE-C2 enhances repair of I-SceI endonuclease-induced DSBs in U-2OS cells. As phosphorylation of KAP1-Ser824 facilitates relaxation of heterochromatin, which is necessary for DNA repair and cellular proliferation, our results suggest that MAGE-C2 can promote tumor growth by phosphorylation of KAP1-Ser824 and by enhancement of DNA damage repair.
authors.affiliation: Department of Medicine, University of Wisconsin, Carbone Cancer Center, Madison, Wisconsin, USA. Electronic address: bjlongley@dermatology.wisc.edu.
authors.forename: Neehar
authors.initials: N
authors.lastname: Bhatia
authors.affiliation: Department of Dermatology, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Tony Z
authors.initials: TZ
authors.lastname: Xiao
authors.affiliation: Department of Dermatology, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Rosenthal
authors.affiliation: Department of Dermatology, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Imtiaz A
authors.initials: IA
authors.lastname: Siddiqui
authors.affiliation: Mazumdar-Shaw Cancer Center, Bangalore, India.
authors.forename: Saravanan
authors.initials: S
authors.lastname: Thiyagarajan
authors.affiliation: Department of Dermatology, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Brendan
authors.initials: B
authors.lastname: Smart
authors.affiliation: McArdle Laboratory for Cancer Research, Madison, Wisconsin, USA.
authors.forename: Qiao
authors.initials: Q
authors.lastname: Meng
authors.affiliation: Department of Medicine, University of Wisconsin, Carbone Cancer Center, Madison, Wisconsin, USA.
authors.forename: Cindy L
authors.initials: CL
authors.lastname: Zuleger
authors.affiliation: Department of Dermatology, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Hasan
authors.initials: H
authors.lastname: Mukhtar
authors.affiliation: McArdle Laboratory for Cancer Research, Madison, Wisconsin, USA.
authors.forename: Shannon C
authors.initials: SC
authors.lastname: Kenney
authors.affiliation: Department of Medicine, University of Wisconsin, Carbone Cancer Center, Madison, Wisconsin, USA; Medical Service, William S. Middleton Memorial Veterans Hospital, Madison, Wisconsin, USA.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Albertini
authors.affiliation: Department of Dermatology, University of Wisconsin, Madison, Wisconsin, USA. Electronic address: bneehar@medicine.wisc.edu.
authors.forename: B
authors.initials: B
authors.lastname: Jack Longley
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000187:drug effects / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000473:pathology*; D002478:Cells, Cultured; D004260:DNA Repair / Q000187:drug effects / Q000502:physiology*; D004273:DNA, Neoplasm / Q000187:drug effects / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D008545:Melanoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008819:Mice, Nude; D009363:Neoplasm Proteins / Q000172:deficiency / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D034741:RNA, Small Interfering / Q000494:pharmacology; D012097:Repressor Proteins / Q000378:metabolism*; D012878:Skin Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D014183:Transplantation, Heterologous; D000076183:Tripartite Motif-Containing Protein 28
chemical_list: D000951:Antigens, Neoplasm; D004273:DNA, Neoplasm; C405429:MAGEC2 protein, human; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; D012097:Repressor Proteins; C101116:TRIM28 protein, human; D000076183:Tripartite Motif-Containing Protein 28