Rat cellular retinol-binding protein: cDNA sequence and rapid retinol-dependent accumulation of mRNA

Cellular retinol-binding protein (CRBP) may be an important mediator of vitamin A action. We report here the identification of a cDNA clone corresponding to the rat CRBP gene. The cDNA is 695 nucleotides long, with an open reading frame corresponding to a protein of 134 amino acids. The deduced amino acid sequence is identical with that of rat CRBP. The nucleotide sequence shows 90.5% similarity with the human CRBP cDNA sequence. Genomic DNA analysis indicates that CRBP is present in one, or at most two, copies within the rat genome. Analysis of mRNA reveals a single species in every tissue tested and suggests that the isolated cDNA is full-length. Finally, when retinol-deficient rats are fed retinyl acetate for 4 hr, about 4-fold accumulation of CRBP-specific mRNA is observed in the lungs. This rapid effect suggests that the micronutrient retinol may directly influence the expression of its specific intracellular binding protein.