REGULATORY ACTIVITIES OF THE 5'-UNTRANSLATED AND 8'-UNTRANSLATED REGIONS AND PROMOTER OF THE HUMAN AGGRECAN GENE

Identification and characterization of the regulatory elements of the human aggrecan gene are necessary first steps in addressing the molecu lar mechanisms through which the gene is regulated. Using luciferase r eporter constructs driven by the human aggrecan pro-meter or the cytom egalovirus promoter, the 5'- and 3'-untranslated regions of the human aggrecan gene were found to regulate gene expression transcriptionally in a promoter- and/or cell type-specific manner. Independent of cell type, the 5'-untranslated region was inhibitory with respect to the cy tomegalovirus promoter, but it was stimulatory to the human aggrecan p romoter. The 5'-untranslated region inhibited the cytomegalovirus prom oter by approximately 60% in both chondrocytes and NIH 3T3 cells, but it stimulated the activity of the human aggrecan promoter about 8-fold in chondrocytes and 40-fold in NIH 3T3 cells, In contrast, the 3'-unt ranslated region inhibited the activities of the human aggrecan promot er by 40-70% in both cell types, but it stimulated the cytomegalovirus promoter activities by 50-60% in NIH 3T3 cells and inhibited its acti vity by 70% in chondrocytes. The differential effects of the untransla ted regions on the two types of promoters may be a reflection of diffe rences in regulation of TATA-less promoters, such as the human aggreca n promoter, and TATA-containing promoters, such as the cytomegalovirus promoter.