title: Histone methyltransferase MLL1 regulates MDR1 transcription and chemoresistance.
abstract: The multidrug resistance 1 gene (MDR1) encodes P-glycoprotein (Pgp), a member of the ATP-binding cassette (ABC) transporter family that confers tumor drug resistance by actively effluxing a number of antitumor agents. We had previously shown that MDR1 transcription is regulated by epigenetic events such as histone acetylation, and had identified the histone acetylase P/CAF and the transcription factor NF-Y as the factors mediating the enzymatic and DNA-anchoring functions, respectively, at the MDR1 promoter. It has also been shown that MDR1 activation is accompanied by increased methylation on lysine 4 of histone H3 (H3K4). In this study, we further investigated histone methylation in MDR1 regulation and function. We show that the mixed lineage leukemia 1 (MLL1) protein, a histone methyltransferase specific for H3K4, is required for MDR1 promoter methylation, as knockdown of MLL1 resulted in a decrease in MDR1 expression. The regulation of MDR1 by MLL1 has functional consequences in that downregulation of MLL1 led to increased retention of the Pgp-specific substrate DIOC(2)(3), as well as increased cellular sensitivity to several Pgp substrates. Regulation of MDR1 by MLL1 was dependent on the CCAAT box within the proximal MDR1 promoter, similar to what we had shown for MDR1 promoter acetylation, and also requires NF-Y. Finally, overexpression of the most prevalent MLL fusion protein, MLL-AF4, led to increased MDR1 expression. This is the first identification of a histone methyltransferase and its leukemogenic rearrangement that regulates expression of an ABC drug transporter, suggesting a new target for circumvention of tumor multidrug resistance.
authors.affiliation: Department of Pharmacology, The Cancer Institute of New Jersey, Robert Wood Johnson Medical School, The University of Medicine and Dentistry of New Jersey, New Brunswick, New Jersey 08901, USA.
authors.forename: Hairong
authors.initials: H
authors.lastname: Huo
authors.forename: Pellegrino G
authors.initials: PG
authors.lastname: Magro
authors.forename: E Christy
authors.initials: EC
authors.lastname: Pietsch
authors.forename: Brijesh B
authors.initials: BB
authors.lastname: Patel
authors.forename: Kathleen W
authors.initials: KW
authors.lastname: Scotto
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics* / Q000378:metabolism; D000107:Acetylation; D000970:Antineoplastic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D023081:CCAAT-Binding Factor / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D019175:DNA Methylation; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D006367:HeLa Cells; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D051788:Myeloid-Lymphoid Leukemia Protein / Q000235:genetics / Q000378:metabolism*; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic / Q000187:drug effects*
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D023081:CCAAT-Binding Factor; D006657:Histones; C113855:MLL-AF4 fusion protein, human; D015514:Oncogene Proteins, Fusion; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051788:Myeloid-Lymphoid Leukemia Protein; D008156:Luciferases; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase