Regulation of the transcriptional activation of CTRP3 in chondrocytes by c-Jun.

Although C1qTNF-related protein 3 (CTRP3) is highly expressed in cartilage and is involved in the proliferation and migration of chondrocytes, the molecular mechanism governing the transcriptional regulation of CTRP3 in chondrocytes is largely unknown. Here, we demonstrated the mechanism of transcriptional activation of the CTRP3 gene in chondrogenic cells. We observed that c-Jun stimulated CTRP3 promoter activity in ATDC5 cells. Deletion analysis of the CTRP3 promoter showed that the c-Jun-responsive region is localized at the position between -359 and -176. Mutation of the AP-1 binding site in this region eliminated c-Jun-mediated CTRP3 promoter activity. A promoter enzyme immunoassay and a chromatin immunoprecipitation assay showed that c-Jun binds directly to the AP-1 binding site at the region -184/-177 of the mouse CTRP3 promoter. Thus, these results demonstrated that c-Jun is a cis-acting element for CTRP3 regulation in chondrogenic cells.