Regulation of human COL9A1 gene expression. Activation of the proximal promoter region by SOX9.

Department of Medicine, Division of Rheumatology, Thomas Jefferson University, Jefferson Medical College, Philadelphia, Pennsylvania 19107, USA.
Journal of Biological Chemistry (Impact Factor: 4.6). 02/2003; 278(1):117-23. DOI: 10.1074/jbc.M208049200
Source: PubMed

ABSTRACT The COL9A1 gene contains two promoter regions, one driving expression of a long alpha1(IX) chain in cartilage (upstream) and one driving expression of a shorter chain in the cornea and vitreous (downstream). To determine how the chondrocyte-specific expression of the COL9A1 gene is regulated, we have begun to characterize the upstream chondrocyte-specific promoter region of the human COL9A1 gene. Transient-transfection analyses performed in rat chondrosarcoma (RCS) cells, human chondrosarcoma (HTB) cells, and NIH/3T3 cells showed that the COL9A1 promoter was active in RCS cells but not HTB or NIH/3T3 cells. Inclusion of the first intron had no effect on promoter activity. In transient-transfection analyses with promoter deletion constructs, it was found that full promoter activity in RCS cells depended on the region from -560 bp to +130 bp relative to the transcriptional start site (+1). Sequence analysis of the region from -890 bp to the transcriptional start predicted five putative SOX/Sry-binding sites. Mutation analysis revealed that two of three putative SOX/Sry binding sites within the -560 to +130 bp region are responsible for most of the COL9A1 promoter activity in RCS cells. Co-transfection experiments with a SOX9 expression plasmid revealed that a construct containing the five putative SOX/Sry-binding sites was transactivated 20- to 30-fold in both HTB and NIH/3T3 cells. Further co-transfection experiments showed that two of the SOX/Sry-binding sites located within the -560 to +130 bp region were required for full transactivation. However, mutation and deletion analyses indicated that a region from -560 to -357 bp, which does not contain any other conspicuous SOX9 sites, is also important for full promoter activity. DNA-protein binding assays and super-shift analysis revealed that SOX9 can form a specific complex with one of the SOX/Sry-binding sites with in the -560 to +130 region.

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