MOLECULAR-CLONING OF A CDNA AND CHROMOSOMAL LOCALIZATION OF A HUMAN THETA-CLASS GLUTATHIONE-S-TRANSFERASE GENE (GSTT2) TO CHROMOSOME-22

Until recently the Theta-class glutathione S-transferases (GSTs) were largely overlooked due to their low activity with the model substrate 1-chloro-2,4-dinitrobenzene (CDNB) and their failure to bind to immobi lized glutathione affinity matrices. Little is known about the number of genes in this class. Recently, Pemble ct al. (Biochem J. 300: 271-2 76, 1994) reported the cDNA cloning of a human Theta-class GST, termed GSTT1. In this study, we describe the molecular cloning of a cDNA enc oding a second human Theta-class GST (GSTT2) from a lambda gt11 human liver 5'-stretch cDNA library. The encoded protein contains 244 amino acids and has 78.3% sequence identity with the rat subunit 12 and only 55.0% identity with human GSTT1. GSTT2 has been mapped to chromosome 22 by somatic cell hybrid analysis. The precise position of the gene w as localized to subband 22q11.2 by in situ hybridization. The absence of other regions of hybridization suggests that there are no closely r elated sequences (e.g., reverse transcribed pseudogenes) scattered thr oughout the genome and that if there are closely related genes, they m ust be clustered near GSTT2. Southern blot analysis of human DNA diges ted with BamHI shows that the size of the GSTT2 gene is relatively sma ll, as the coding sequence falls within a 3.6-kb BamHI fragment. (C) 1 995 Academic Press, Inc.