A SINGLE-MOUSE GLUTATHIONE SYNTHETASE GENE ENCODES 6 MESSENGER-RNAS WITH DIFFERENT 5'-END

To understand more about the role of glutathione (GSH) in metabolism, we have cloned both cDNA and genomic sequences for mouse gIutathione s ynthetase (GSH syn), the enzyme that catalyzes the last step in the sy nthesis of glutathione. The mouse cDNA contains an open reading frame (ORF) of 474 aa and shares 64 and 95% deduced amino acid sequence iden tity with Xenopus cDNA and rat cDNA, respectively. The cDNA complement s Schizosaccaromyces pombe strains deficient in GSH syn. The gene is a single-copy gene spanning similar to 30 kb and is composed of at leas t 15 exons. Steady-state RNA levels and enzyme activity levels are hig hest in kidney, about 3-fold lower in liver, and 8- to 10-fold lower i n lung and brain. We have identified six different GSH syn RNAs: three , termed types Al, A2, and A3, have different 5' ends that localize to different sites in the gene, but appear to encode the same protein (4 74 aa). Types B, C1, and C2 all have unique 5' ends and type-specific ORFs, which are shorter than that for types Al, A2, and A3. In liver o nly type Al GSH syn RNA is detectable, while in kidney 90% of GSH syn RNA is type Al and types B and C account for about 10%. (C) 1996 Acade mic Press, Inc.