THE MURINE GENE FOR CELLULAR RETINOIC ACID-BINDING PROTEIN TYPE-II - GENOMIC ORGANIZATION, CHROMOSOMAL LOCALIZATION, AND POSTTRANSCRIPTIONAL REGULATION BY RETINOIC ACID

The cellular retinoic acid-binding protein type II (CRABP-II) is a member of the serum and cytoplasmic retinoid-binding protein family. It is expressed during embryonic development and in adult skin and is up-regulated by retinoic acid (RA) in F9 teratocarcinoma cells. We have determined the genomic organization of the murine CRABP-II gene and performed a detailed analysis of its transcriptional unit. The CRABP-II gene, located on mouse chromosome 2, is approximately 4.6 kilobases long and divided into four exons in a structure common to other members of the family of serum and cellular retinoid-binding proteins. Primer extension analysis and S1 nuclease protection assay were used to identify the transcription initiation site which is located 27 base pairs downstream of a typical TATAA box. Sequence analysis of the promoter also revealed a GC-rich region with overlapping putative SP1-binding sites at nucleotides -61 and AP-1 and AP-2-binding sites at nucleotides -518 and -544, respectively. The 3'-untranslated region contains two copies of the pentanucleotide AUUUA shown to be involved in messenger RNA destabilization. Consensus sequence for retinoic acid response elements were not detected in the promoter region of the CRABP-II gene. Results of nuclear run on experiments show that the CRABP-II gene is not transcriptionally activated by RA in F9 teratocarcinoma cells. These results suggest that the up-regulation of CRABP-II mRNA levels by RA is mainly controlled by a post-transcriptional mechanism.