Differential regulation of the carbonic anhydrase II gene expression by hormonal nuclear receptors in monocytic cells: Identification of the retinoicacid response element

The Carbonic Anhydrase LI (CAII) gene that encodes an enzyme involved in pr oton production is expressed in several cell types including monocyte/macro phage-derived osteoclasts. We have analyzed the regulation of the chicken C ATI promoter/reporter construct by nuclear hormone receptors of the VDR sub family in HD11 avian macrophages. The CAII expression is stimulated by 1,25 -dihydroxyvitamin D-3 but not by 9-cis retinoic acid and repressed by VDR o verexpression due to RXR squelching. It is also stimulated by all-trans ret inoic acid only when RAR alpha is overexpressed, and is dependent on a RARE located in the distal part of the promoter and bound by RAR alpha homodime r. Finally, in macrophages, unlike in erythrocytes, the CAII promoter is un responsive to thyroid hormone. Our results demonstrate the first retinoic a cid response element in the CAII promoter and show that according to cell t ype, different nuclear receptors of the VDR subfamily can regulate the CAII gene. (C) 2000 Academic Press.