title: A chemical biology screen identifies glucocorticoids that regulate c-maf expression by increasing its proteasomal degradation through up-regulation of ubiquitin.
abstract: The oncogene c-maf is frequently overexpressed in multiple myeloma cell lines and patient samples and contributes to increased cellular proliferation in part by inducing cyclin D2 expression. To identify regulators of c-maf, we developed a chemical screen in NIH3T3 cells stably overexpressing c-maf and the cyclin D2 promoter driving luciferase. From a screen of 2400 off-patent drugs and chemicals, we identified glucocorticoids as c-maf-dependent inhibitors of cyclin D2 transactivation. In multiple myeloma cell lines, glucocorticoids reduced levels of c-maf protein without influencing corresponding mRNA levels. Subsequent studies demonstrated that glucocorticoids increased ubiquitination-dependent degradation of c-maf and up-regulated ubiquitin C mRNA. Moreover, ectopic expression of ubiquitin C recapitulated the effects of glucocorticoids, demonstrating regulation of c-maf protein through the abundance of the ubiquitin substrate. Thus, using a chemical biology approach, we identified a novel mechanism of action of glucocorticoids and a novel mechanism by which levels of c-maf protein are regulated by the abundance of the ubiquitin substrate.
authors: Princess Margaret Hospital, Ontario Cancer Institute, Toronto, ON, Canada.
authors: Xinliang
authors: X
authors: Mao
authors: A Keith
authors: AK
authors: Stewart
authors: Rose
authors: R
authors: Hurren
authors: Alessandro
authors: A
authors: Datti
authors: Xuegong
authors: X
authors: Zhu
authors: Yuanxiao
authors: Y
authors: Zhu
authors: Changxin
authors: C
authors: Shi
authors: Kyle
authors: K
authors: Lee
authors: Rodger
authors: R
authors: Tiedemann
authors: Yanina
authors: Y
authors: Eberhard
authors: Suzanne
authors: S
authors: Trudel
authors: Shengben
authors: S
authors: Liang
authors: Seth J
authors: SJ
authors: Corey
authors: Lisa C
authors: LC
authors: Gillis
authors: Dwayne L
authors: DL
authors: Barber
authors: Jeffery L
authors: JL
authors: Wrana
authors: Shereen
authors: S
authors: Ezzat
authors: Aaron D
authors: AD
authors: Schimmer
mesh_terms: D000818:Animals; D056742:Cyclin D2; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D004353:Drug Evaluation, Preclinical; D005938:Glucocorticoids / Q000737:chemistry / Q000494:pharmacology*; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D011401:Promoter Regions, Genetic / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D051257:Proto-Oncogene Proteins c-maf / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects; D025801:Ubiquitin / Q000378:metabolism*; D054875:Ubiquitination / Q000187:drug effects*; D015854:Up-Regulation / Q000187:drug effects*
chemical_list: C486196:Ccnd2 protein, mouse; D056742:Cyclin D2; D016213:Cyclins; D005938:Glucocorticoids; C495608:Maf protein, mouse; D051257:Proto-Oncogene Proteins c-maf; D025801:Ubiquitin; D008156:Luciferases; D046988:Proteasome Endopeptidase Complex