Induction of basic helix-loop-helix protein DEC1 (BHLHB2)/Stra13/Sharp2 in reponse to the cyclic adenosine monophosphate pathway

DEC1 (BHLHB2)/Stra13/Sharp2, a basic helix-loop-helix (bHLH) transcription factor has been suggested to be involved in the control of proliferation and/or differentiation of several cells including nerve cells, fibroblast and chondrocytes. In the present study, we examined the effect of parathyroid hormone (PTH), dibutyryl cAMP (Bt₂cAMP) and forskolin on the expression of DEC1 in various cells. In rabbit chondrocyte cultures, PTH or Bt₂cAMP increased the DEC1 mRNA level within 1 h. Thereafter, the DEC1 mRNA level rapidly decreased to the basal level at 3 h, and increased at 6-24 h. In cultures of a mouse embryo prechondrogenic cell line ATDC5, PTH or forskolin, and activator of adenylate cyclase, also increased the DEC1 mRNA level within 1 h. Furthermore, in all evaluated cell lines of human fibroblasts, canine epithelial cells, human carcinoma, human glioblastoma and human melanoma, Bt₂cAMP increased the DEC1 mRNA level within 1-3 h. Studies with actinomycin D and cycloheximide indicated that the enhancement of DEC1 mRNA by cAMP was not due to mRNA stabilization and did not require new protein synthesis. These findings suggest that DEC1 is a novel direct target for cAMP in wide types of cells, and that the bHLH protein is involved in the control of gene expression in cAMP-activated cells.