title: Genomic structure of rat 3alpha-hydroxysteroid/dihydrodiol dehydrogenase (3alpha-HSD/DD, AKR1C9).
abstract: Rat liver 3alpha-hydroxysteroid/dihydrodiol dehydrogenase (3alpha-HSD/DD) is a member of the aldo-keto reductase (AKR) superfamily. It is involved in the inactivation of steroid hormones and the metabolic activation of polycyclic aromatic hydrocarbons (PAH) by converting trans-dihydrodiols into reactive and redox-active o-quinones. The structure of the 5'-flanking region of the gene and factors involved in the constitutive and regulated expression of this gene have been reported [H.-K. Lin, T.M. Penning, Cloning, sequencing, and functional analysis of the 5'-flanking region of the rat 3alpha-hydroxysteroid/dihydrodiol dehydrogenase gene, Cancer Res. 55 (1995) 4105-4113]. We now describe the complete genomic structure of the rat type 1 3alpha-HSD/DD gene. Charon 4A and P1 genomic clones contained at least three rat genes (type 1, type 2 and type 3 3alpha-HSD/DD) each of which encoded for the same open reading frame (ORF) but differed in their exon-intron organization. 5'-RACE confirmed that the type 1 3alpha-HSD/DD gene encodes for the dominant transcript in rat liver and it was the regulation of this gene that was previously studied. The rat type 1 3alpha-HSD/DD gene is 30 kb in length and consists of nine exons and eight introns. Exon 9 encodes +931 to 966 bp of the ORF and the 1292 bp 3'-UTR implicated in mRNA stability. This genomic structure is nearly identical to the homologous human genes, type 1 3alpha-HSD (chlordecone reductase/DD4, AKR1C4), type 2 3alpha-HSD (AKR1C3) and type 3 3alpha-HSD (bile-acid binding protein, AKR1C2) genes. Three different cDNA's containing identical ORFs for 3alpha-HSD have been reported suggesting that all three genes may be expressed in rat liver. Using 5' primers corresponding to the 5'-UTR's of the three different cDNA's only one PCR fragment was obtained and corresponded to the type 1 3alpha-HSD/DD gene. These data suggested that the type 2 and type 3 3alpha-HSD/DD genes are not abundantly expressed in rat liver. It is unknown whether the type 2 and type 3 3alpha-HSD/DD genes represent pseudo-genes or whether they represent genes that are differentially expressed in other rat tissues.
authors.affiliation: Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104-6084, USA.
authors.forename: H K
authors.initials: HK
authors.lastname: Lin
authors.forename: C F
authors.initials: CF
authors.lastname: Hung
authors.forename: M
authors.initials: M
authors.lastname: Moore
authors.forename: T M
authors.initials: TM
authors.lastname: Penning
mesh_terms: D020413:3' Untranslated Regions; D015096:3-Hydroxysteroid Dehydrogenases / Q000235:genetics*; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); D020121:5' Untranslated Regions; D000818:Animals; D001435:Bacteriophages / Q000235:genetics; D005091:Exons; D005260:Female; D020869:Gene Expression Profiling; D015723:Gene Library; D005821:Genetic Techniques; D006801:Humans; D006913:Hydroxysteroid Dehydrogenases / Q000235:genetics*; D007438:Introns; D008099:Liver / Q000502:physiology; D008297:Male; D008969:Molecular Sequence Data; D005810:Multigene Family; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic
chemical_list: D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; C403192:3-hydroxysteroid dihydrodiol dehydrogenase; D015096:3-Hydroxysteroid Dehydrogenases; D006913:Hydroxysteroid Dehydrogenases; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)