title: Interaction of HIF and USF signaling pathways in human genes flanked by hypoxia-response elements and E-box palindromes.
abstract: Rampant activity of the hypoxia-inducible factor (HIF)-1 in cancer is frequently associated with the malignant progression into a harder-to-treat, increasingly aggressive phenotype. Clearly, anti-HIF strategies in cancer cells are of considerable clinical interest. One way to fine-tune, or inhibit, HIF's transcriptional outflow independently of hydroxylase activities could be through competing transcription factors. A CACGTG-binding activity in human hepatoma cells was previously found to restrict HIF's access to hypoxia response cis-elements (HRE) in a Daphnia globin gene promoter construct (phb2). The CACGTG factor, and its impact on hypoxia-responsive human genes, was analyzed in this study by genome-wide computational scans as well as gene-specific quantitative PCR, reporter and DNA-binding assays in hepatoma (Hep3B), cervical carcinoma (HeLa), and breast carcinoma (MCF7) cells. Among six basic helix-loop-helix transcription factors known to target CACGTG palindromes, we identified upstream stimulatory factor (USF)-1/2 as predominant phb2 CACGTG constituents in Hep3B, HeLa, and MCF7 cells. Human genes with adjacent or overlapping HRE and CACGTG motifs included with lactate dehydrogenase A (LDHA) and Bcl-2/E1B 19 kDa interacting protein 3 (BNIP3) hypoxia-induced HIF-1 targets. Parallel recruitment of HIF-1α and USF1/2a to the respective promoter chromatin was verified for all cell lines investigated. Mutual complementing (LDHA) or moderating (BNIP3) cross-talk was seen upon overexpression or silencing of HIF-1α and USF1/2a. Distinct (LDHA) or overlapping (BNIP3) promoter-binding sites for HIF-1 and USFs were subsequently characterized. We propose that, depending on abundance or activity of its protein constituents, O(2)-independent USF signaling can function to fine-tune or interfere with HIF-mediated transcription in cancer cells.
authors: Institute of Veterinary Physiology, University of Zurich, Zurich, Switzerland.
authors: Junmin
authors: J
authors: Hu
authors: Daniel P
authors: DP
authors: Stiehl
authors: Claudia
authors: C
authors: Setzer
authors: Daniela
authors: D
authors: Wichmann
authors: Dheeraj A
authors: DA
authors: Shinde
authors: Hubert
authors: H
authors: Rehrauer
authors: Pavel
authors: P
authors: Hradecky
authors: Max
authors: M
authors: Gassmann
authors: Thomas A
authors: TA
authors: Gorr
mesh_terms: D045744:Cell Line, Tumor; D024721:E-Box Elements; D005260:Female; D006367:HeLa Cells; D006801:Humans; D051793:Hypoxia-Inducible Factor 1 / Q000235:genetics* / Q000378:metabolism; D055029:Inverted Repeat Sequences; D000091402:Prohibitins; D020218:Response Elements; D015398:Signal Transduction; D014162:Transfection; D051720:Upstream Stimulatory Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D051793:Hypoxia-Inducible Factor 1; C000717331:PHB2 protein, human; D000091402:Prohibitins; C497181:USF1 protein, human; C497184:USF2 protein, human; D051720:Upstream Stimulatory Factors