Hypoxic regulation of stability of connective tissue growth factor/CCN2 mRNA by 3′-untranslated region interacting with a cellular protein in human chondrosarcoma cells

Connective tissue growth factor (CTGF/CCN2) can be induced by various forms of stress such as exposure to high glucose, mechanical load, or hypoxia. Here, we investigated the molecular mechanism involved in the induction of ctgf/ccn2 by hypoxia in a human chondrosarcoma cell line, HCS-2/8. Hypoxia increased the ctgf/ ccn2 mRNA level by altering the 3′-untranslated region (UTR)-mediated mRNA stability without requiring de novo protein synthesis. After a series of extensive analyses, we eventually found that the cis-repressive element of 84 bases within the 3′-UTR specifically bound to a cytoplasmic/nuclear protein. By conducting a UV crosslinking assay, we found the cytoplasmic/nuclear protein to be a 35 kDa molecule that bound to the cis-element in a hypoxia-inducible manner. These results suggest that a cis-element in the 3′-UTR of ctgf/ccn2 mRNA and trans-factor counterpart(s) play an important role in the post-transcriptional regulation by determining the stability of ctgf/ccn2 mRNA.