A novel retinoic acid-response element requires an enhancer element mediator for transcriptional activation.
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.
Harris
Laura R
LR
Department of Microbiology and Molecular Biology, Brigham Young University, 591 WIDB, Provo, UT 84602, USA.
Kamarainen
Olli-Pekka
OP
Sevakivi
Minna
M
Miller
Gwen C
GC
Clarke
James W
JW
Potter
Jennifer L
JL
Bridgewater
Laura C
LC
D000818:Animals; D001483:Base Sequence; D019902:Chondrocytes / Q000378:metabolism; D024161:Collagen Type XI / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000502:physiology*; D051379:Mice; D051381:Rats; D020218:Response Elements / Q000502:physiology*; D049230:Retinoid X Receptor beta / Q000378:metabolism; D017384:Sequence Deletion; D015533:Transcriptional Activation / Q000502:physiology*; D014212:Tretinoin / Q000502:physiology*; D014407:Tumor Cells, Cultured
C497046:Col11a2 protein, mouse; D024161:Collagen Type XI; D004268:DNA-Binding Proteins; D049230:Retinoid X Receptor beta; D014212:Tretinoin