HUMAN MN CA9 GENE, A NOVEL MEMBER OF THE CARBONIC-ANHYDRASE FAMILY - STRUCTURE AND EXON TO PROTEIN DOMAIN RELATIONSHIPS/

We have isolated, sequenced, and characterized a human MN/CA9 gene. Th is gene is a novel member of the carbonic anhydrase (CA) family, which codes for widely distributed catalysts of the reversible conversion o f carbon dioxide to carbonic acid. So far, MN/CA IX is the only tumor- associated CA isoenzyme. The entire genomic sequence of MN/CA9, includ ing the 5'-flanking region, encompasses 10.9 kb. The coding sequence i s divided into 11 exons, whose organization and relationships to predi cted protein domains suggest that the gene arose by exon shuffling. Ex on 1 encodes a signal peptide and a proteoglycan-related region. Exons 2-8 code for a CA domain with a highly conserved active site. The exo n/intron pattern of the CA coding region is similar but not identical to other described animal kingdom alpha-CA genes. Exons 10 and 11 enco de a transmembrane anchor and an intracytoplasmic tail, respectively. We have also determined the transcription initiation and termination s ites by RNase protection assay and analyzed the 3.5-kb, region upstrea m of the MN/CA9 gene. Sequence of the proximate 5' end of the flanking region shows extensive homology to the long terminal repeats of HERV- K endogenous retroviruses. The putative MN/CA9 promoter immediately pr eceding the transcription start site does not possess a TATA box, but contains consensus sequences for the AP1, AP2, p53, and hn transcripti on factors. This study will allow further investigations of the molecu lar events regulating expression of MN/CA IX as well as elucidation of its biological function. (C) 1996 Academic Press, Inc.