STRUCTURE OF THE HUMAN CELLULAR RETINOIC ACID-BINDING PROTEIN-II GENE - EARLY TRANSCRIPTIONAL REGULATION BY RETINOIC ACID

The gene for human cellular retinoic acid-binding protein II (CRABP-II) has been cloned. It was isolated from a human placenta genomic library and is contained within one bacteriophage clone. The gene spans 6 kilobases and consists of 4 exons. One major transcription initiation site was mapped to an A residue 137 nucleotides upstream of the ATG initiation codon. The upstream region contains a TATA box and potential AP2, Sp1, and Krox-24 binding sites, as well as a direct repeat with homology to a retinoic acid-responsive element. The CRABP-II mRNA was rapidly induced within 2-6 h in cultured human skin fibroblasts by retinoic acid, reaching a plateau after 6 h of treatment. The rapid increase of CRABP-II message was mainly due to an increased rate of transcription as determined by nuclear run-on experiments. Increased transcription could be detected as early as 1 h after addition of retinoic acid, peaked at 2 h, and returned to basal levels within 6 h. On-going protein synthesis was required for this transient increase of transcription, since the induction was blocked by cycloheximide. These data suggest that the human CRABP-II gene is transcriptionally regulated by a newly synthesized regulatory protein.