THE HUMAN EPRS LOCUS (FORMERLY THE QARS LOCUS) - A GENE ENCODING A CLASS-I AND A CLASS-II AMINOACYL-TRANSFER-RNA SYNTHETASE

Glutamyl-tRNA synthetase and prolyl-tRNA synthetase belong to differen t classes of aminoacyl-tRNA synthetases that are thought to have evolv ed along independent evolutionary pathways. However, both enzymes are on one polypeptide chain encoded by a single human gene, the EPRS locu s, which is transcribed as one long mRNA. me report the structure of t he human EPRS gene, which consists of 29 exons spread over at least 90 kb of genomic DNA. The exons, encoding the glutamylspecific and the p rolyl-specific parts of the enzyme, are each clustered in 10-kb sectio ns located at opposite ends of the gene. These two exon clusters are s eparated by a long intervening DNA section with a number of exons, enc oding functions that may be involved in the organization of the mammal ian multienzyme synthetase complex. The upstream gene region shows str uctural features of a regulated gene, and preliminary experiments sugg est that the gene is expressed at specific times in growth-stimulated cultured cells. me have localized the gene to the distal long arm of h uman chromosome 1 and to a corresponding site in mouse chromosome 1. ( C) 1994 Academic Press, Inc.