Abstract:

Objective To study the effects of hypoxia-inducible factor 1α (HIF-1α) on the regulation of transcription factor KLF5 expression and on the cell proliferation. Methods 293T cells were treated with hypoxia (1% O2 or hypoxia mimic CoCl2) and the mRNA and protein levels of HIF-1α and KLF5 were detected with the use of real-time qPCR and Western blotting. The HIF-1α expression was inhibited with shRNA and the KLF5 expression was detected after 293T cells were treated with hypoxia. The HIF-1α-P2A plasmid in 293T cells was over-expressed and the effects of which on expressions of KLF5 promoter-driven luciferase and KLF5 were detected. HIF-1α-P2A-overexpressed 293T cells were transfected with shKLF5 and the cell proliferation was detected with CCK8. 293T cells were co-transfected with KLF5 plasmid and HRE-luciferase plasmid, and the effects of KLF5 expression on HIF-1α transcriptional activity was evaluated with the luciferase reporter system. Results qPCR and Western blotting showed that hypoxia treatment could stabilize HIF-1α protein and transcriptionally upregulate the KLF5 expression. Inhibition of HIF-1α expression with shRNA could suppress hypoxia-induced up-regulation of KLF5 expression. Over-expressed exogenous HIF-1α-P2A could directly bind to the promoter region of KLF5 and up-regulate KLF5 expression. Although over-expression of HIF-1α-P2A or inhibition of shKLF5 alone was unable to affect cell proliferation, their combination could significantly promote cell proliferation. Overexpressed KLF5 could significantly inhibit the transcriptional activity of HIF-1α. Conclusion KLF5 is the direct target gene of HIF-1α and HIF-1α transcriptionally regulates the KLF5 expression. KLF5 may inhibit the HIF-1α-promoted cell proliferation via suppressing the transcriptional activity of HIF-1α.

Key words: HIF-1α, KLF5, hypoxia, cell proliferation