Two nuclear retinoid receptors that were expressed in bacteria, retinoic acid receptor-gamma and retinoid X receptor-alpha, were found to bind specifically to a double-stranded oligonucleotide containing the RARE in gel mobility shift assays. Computer sequence analysis of the 3.6-kb DNA fragment that contains the promoter for the rat pro alpha1(I) collagen gene identified a direct repeat RARE sequence composed of one diverse (5'-AGTAGA-3') and one idealized (5'-GGGTCA-3') half site located at positions -1345 and -1335, respectively. Transforming growth factor-beta1 did not block the inhibitory effect of t-RA on CAT activity. Maximal inhibition of CAT activity by t-RA occurred at 10(-8) M after 48 h of treatment.
The effect of t-RA on CAT activity was determined as a function of concentration and incubation time. FRS fibroblasts were stably transfected with the ColCat3.6 plasmid, which contains a portion of the 5' flanking region of the rat pro alpha1(I) collagen gene linked to a reporter gene, chloramphenicol acetyltransferase.
The current study was undertaken to determine the mechanism by which the retinoid all-trans-retinoic acid regulates pro alpha1(I) collagen gene expression in fetal rat skin fibroblasts.
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