Alpha 2(I) collagen gene expression is up-regulated in quail chondrocytes pretreated with retinoic acid

alpha 2(I) collagen gene expression is induced in quail embryo chondrocytes pretreated with retinoic acid (RA). The initial appearance of alpha 2(I) mRNA occurs around day 3 of culture in RA-free medium and rapidly progresses over the next 4 days. In transient transfection assays, expression of COL1A2-CAT, a chimeric gene bearing 3500 bp upstream the bone/tendon transcription start site from the human alpha 2(I) gene fused to the CAT gene, is stimulated severalfold in RA-treated chondrocytes. In contrast, enzyme activity is very low in untreated chondrocytes, suggesting that the sequences required for RA-induced transcription of the alpha 2(I) gene are present in this plasmid. Analysis of alpha 2(I) promoter sequences performed with deletion mutants gives overlapping results in collagen type I-producing fibroblasts and chondrocytes withdrawn from RA treatment. These experiments suggest that RA-induced transcription of the alpha 2(I) collagen gene in chondrocytes is regulated by the binding of transcription factors to the same regulatory sequences that control transcription in fibroblasts.