FP16-2 Regulation of CDKN2B Expression by Interaction of Arnt with Miz-1 - A Basis for Functional Integration Between the HIF and Myc Gene Regulatory Pathways

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: FP16-Cancers of Endocrine Organs: Mechanisms of Tumorigenesis & Progression
Sunday, June 16, 2013: 10:45 AM-11:15 AM
Presentation Start Time: 10:50 AM
Room 206 (Moscone Center)

Poster Board SUN-303
Reidun Aesoey*1, Katarina Gradin2, Kathrine Aasrud1, Erling Andre Hoivik1, Jorge L Ruas2, Lorenz Poellinger2 and Marit Bakke1
1University of Bergen, Norway, 2Karolinska Institutet, Sweden
Hypoxia- and Myc-dependent transcriptional regulatory pathways are frequently deregulated in cancer cells. These pathways converge in many cellular responses, but the underlying molecular mechanisms are unclear. In the present study we demonstrate that the aryl hydrocarbon nuclear translocator (Arnt), which is central in hypoxia-induced signaling, forms a complex with Miz-1, an important transcriptional regulator in Myc-mediated transcriptional repression. Overexpression of Arnt induced reporter genes driven by the proximal promoter of the gene encoding cyclin-dependent kinase inhibitor 2B (CDKN2B), which is an established target for the Myc/Miz-1 complex, whereas mutated forms of Arnt that were unable to interact with Miz-1, had reduced capability to activate transcription. Moreover, repression of Arnt reduced endogenous CDKN2B expression, and chromatin immunoprecipitation demonstrated that Arnt interacts with the CDKN2B promoter. The Arnt/Miz-1 interaction surface involves helix II of the helix-loop-helix domain of Arnt, suggesting a similar mode of interaction as for Myc/Miz-1. The transcriptional activity of Arnt was counteracted by Myc, but not by a mutated variant of Myc that is unable to interact with Miz-1, suggesting mutually exclusive interaction of Arnt and Myc with Miz-1. Our data also establish CDKN2B as a hypoxia regulated gene, as endogenous CDKN2B mRNA levels were reduced by hypoxic treatment of U2OS cells and after down-regulation of hypoxia-inducible-factors-1a and -2a. Our results reveal a novel mode of regulation by protein-protein interaction that directly ties together, at the transcriptional level, the Myc- and hypoxia-dependent signaling pathways and expands our understanding of the roles of hypoxia and cell cycle alterations during tumorigenesis.

Nothing to Disclose: RA, KG, KA, EAH, JLR, LP, MB

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: This work was supported by the National Program for Research in Functional Genomics in Norway (FUGE) in the Research Council of Norway and the Meltzer Foundation (M.B.).