title: MAGE I transcription factors regulate KAP1 and KRAB domain zinc finger transcription factor mediated gene repression.
abstract: Class I MAGE proteins (MAGE I) are normally expressed only in developing germ cells but are aberrantly expressed in many cancers. They have been shown to promote tumor survival, aggressive growth, and chemoresistance but the underlying mechanisms and MAGE I functions have not been fully elucidated. KRAB domain zinc finger transcription factors (KZNFs) are the largest group of vertebrate transcription factors and regulate neoplastic transformation, tumor suppression, cellular proliferation, and apoptosis. KZNFs bind the KAP1 protein and direct KAP1 to specific DNA sequences where it suppresses gene expression by inducing localized heterochromatin characterized by histone 3 lysine 9 trimethylation (H3me3K9). Discovery that MAGE I proteins also bind to KAP1 prompted us to investigate whether MAGE I can affect KZNF and KAP1 mediated gene regulation. We found that expression of MAGE I proteins, MAGE-A3 or MAGE-C2, relieved repression of a reporter gene by ZNF382, a KZNF with tumor suppressor activity. ChIP of MAGE I (-) HEK293T cells showed KAP1 and H3me3K9 are normally bound to the ID1 gene, a target of ZNF382, but that binding is greatly reduced in the presence of MAGE I proteins. MAGE I expression relieved KAP1 mediated ID1 repression, causing increased expression of ID1 mRNA and ID1 chromatin relaxation characterized by loss of H3me3K9. MAGE I binding to KAP1 also induced ZNF382 poly-ubiquitination and degradation, consistent with loss of ZNF382 leading to decreased KAP1 binding to ID1. In contrast, MAGE I expression caused increased KAP1 binding to Ki67, another KAP1 target gene, with increased H3me3K9 and decreased Ki67 mRNA expression. Since KZNFs are required to direct KAP1 to specific genes, these results show that MAGE I proteins can differentially regulate members of the KZNF family and KAP1 mediated gene repression.
authors.affiliation: Department of Dermatology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America. Txiao@dermatology.wisc.edu
authors.forename: Tony Z
authors.initials: TZ
authors.lastname: Xiao
authors.forename: Neehar
authors.initials: N
authors.lastname: Bhatia
authors.forename: Raul
authors.initials: R
authors.lastname: Urrutia
authors.forename: Gwen A
authors.initials: GA
authors.lastname: Lomberk
authors.forename: Andrew
authors.initials: A
authors.lastname: Simpson
authors.forename: B Jack
authors.initials: BJ
authors.lastname: Longley
mesh_terms: D000951:Antigens, Neoplasm / Q000378:metabolism*; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D057809:HEK293 Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D051798:Inhibitor of Differentiation Protein 1 / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D008745:Methylation; D008954:Models, Biological; D050505:Mutant Proteins / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D015203:Reproducibility of Results; D014157:Transcription Factors / Q000378:metabolism*; D000076183:Tripartite Motif-Containing Protein 28; D054875:Ubiquitination; D016335:Zinc Fingers
chemical_list: D000951:Antigens, Neoplasm; D004268:DNA-Binding Proteins; D006657:Histones; C497453:ID1 protein, human; D051798:Inhibitor of Differentiation Protein 1; C072013:MAGEA3 protein, human; C405429:MAGEC2 protein, human; D050505:Mutant Proteins; D009363:Neoplasm Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C116326:ZNF382 protein, human; C101116:TRIM28 protein, human; D000076183:Tripartite Motif-Containing Protein 28; D008239:Lysine