A novel retinoic acid-response element requires an enhancer element mediator for transcriptional activation

• Published in: Biochemical journal 2004-10, Vol.383 (Pt 1), p.37-43
• Main Authors: Harris, Laura R, Kamarainen, Olli-Pekka, Sevakivi, Minna, Miller, Gwen C, Clarke, James W, Potter, Jennifer L, Bridgewater, Laura C
• Format: Article
• Language: English
• Subjects: Animals; Base Sequence; Chondrocytes - metabolism; Collagen Type XI - genetics; DNA-Binding Proteins - metabolism; Enhancer Elements, Genetic - physiology; Mice; Rats; Response Elements - physiology; Retinoid X Receptor beta - metabolism; Sequence Deletion; Transcriptional Activation - physiology; Tretinoin - physiology; Tumor Cells, Cultured
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/BJ20040715

The Col11a2 gene codes for alpha2(XI), a subunit of type XI collagen that is a critical component of the cartilage extracellular matrix. The 5' regulatory region of Col11a2 was subjected to deletional analysis to detect any regulatory element in addition to the two known chondrocyte-specific enhancer elements B/C and D/E. Deletion of the region from -342 to -242 bp reduced transcriptional activity to less than 50% of wild-type, but the sequence showed no independent ability to increase transcription from a minimal promoter. When cloned downstream of the D/E enhancer, however, a subsection of the sequence nearly doubled transcriptional activity and produced an additional 3-fold activation in response to RA (retinoic acid). A 6-bp direct repeat, separated by 4 bp (a DR-4 element) near the 5'-end of this region, was found to be essential for its activity, and was further shown to bind the RA X receptor beta in electrophoretic mobility-shift assays. The present study has revealed a novel RA-response element in Col11a2 that does not interact directly with the promoter, but instead requires the D/E enhancer to mediate transcriptional activation. Proteins bound at the enhancer, therefore, would be expected to affect the transcriptional response to RA. Such a system of regulation, particularly if found to be operating in other cartilage genes, could explain the conflicting responses RA produces in chondrocytes under different experimental conditions.