The genomic structure of human olfactory receptor genes

The genomic and cDNA structures were studied for eight human olfactory rece ptor (OR) genes within the chromosome 17p13.3 cluster. A common gene struct ure was revealed, which included an similar to1-kb intronless coding region terminated by a signal for polyadenylation and a variable number of upstre am noncoding exons. The latter were found to be alternatively spliced, givi ng rise to different isoforms of OR mRNA. While the initial exons mostly ag reed with previous computer predictions and were conserved within OR subfam ilies, other upstream exons were novel and idiosyncratic. In some cases, re petitive sequences were involved in the generation of splice sites and puta tive transcription control elements. Such gene structure is consistent with early repertoire enhancement by retrogene generation, which was likely fol lowed by extensive genomic duplication. Each OR gene had a unique signature of transcription factor elements, consistent with a combinatorial expressi on control mechanism. (C) 2000 Academic Press.