Virus-based reporter systems for monitoring transcriptional activity of hypoxia-inducible factor 1

Being key regulator of oxygen homeostasis hypoxia-inducible factor 1 (HIF-1) plays significant roles in cancer progression as well as in cardiovascular diseases. The modulation of HIF-1α activity in vivo may represent a valuable therapeutic approach to these disorders [Hofer, T., Desbaillets, I., Hopfl, G., Wenger, R.H., Gassmann, M., 2002. Characterization of HIF-1 alpha overexpressing HeLa cells and implications for gene therapy. Comp. Biochem. Physiol., Toxicol. Pharmacol. 133, 475-481]. In order to monitor HIF-1 transcriptional activity, we have developed HIF-1α-responsive reporter constructs, in which lacZ gene expression is driven by minimal Hsp70 gene promoter or minimal immediate early promoter of cytomegalovirus (CMV) and a combination of hypoxia response elements from regulatory regions of PGK1, ENO1 and LDHA genes. For the efficient delivery to a wide variety of cell types we chose retroviral and lentiviral vectors as carriers of the reporter cassette. We demonstrate that the obtained reporter system i) has a high inducibility in response to treatments leading to HIF-1α activation, ii) shows upregulation in response to HIF-1 activation and downregulation following inhibition of HIF-1α expression by small interfering RNA, iii) follows the dynamics of endogenous HIF-1 target gene expression. The retrovirus- and lentivirus-based reporters can be used for high-throughput screening of HIF-1α modulators and for the study of crosstalk between HIF-1 and different related signal transduction pathways. Potential applications for the reporters are discussed.