STRUCTURE OF THE HUMAN RETINOIC ACID RECEPTOR BETA-1 GENE

We report the isolation and characterization of genomic sequences codi ng for the 5' end of human retinoic acid receptor beta 1, a fetal RAR isoform which is also expressed in small cell lung cancers. Primer ext ension analysis revealed a principal transcription start site with a s econdary site 23 bp further upstream in both SCLC and fetal tissues. T he sequences isolated were CpG-rich between -60 and the 3' end of the first exon but there were no features like a TATA-box or an Inr elemen t. In several important aspects, the human RAR beta 1 differs from its mouse counterpart. The 5'-UTR is 823 bp long and is encoded by four e xons (vs two in the mouse giving a 477 bp UTR). The 5' end of the mous e cDNA has been mapped to a 67 bp CT repeat which is absent in our seq uences. We were also unable to find evidence for a human isoform RAR b eta 3 which is widely expressed in mouse tissues.