GSTM1 (Glutathione S-transferase M1)

Abstract

The GSTM1 gene is composed of 8 exons spanning a region of 21,244 bases, with transcript length of 1,161 bps and translation length of 218 residues (according to ensembl GRCh37 release 78). The GSTM1 gene is approximately 20 kb in length and is closely flanked by other mu class gene sequences. The end points of the polymorphic GSTM1 deletion are: the left repeated region 5 kb downstream from the 3?-end of the GSTM2 gene and 5 kb upstream from the beginning of the GSTM1 gene; the right repeated region 5 kb downstream from the 3?-end of the GSTM1 and 10 kb upstream from the 5?-end of the GSTM5 gene (Xu et al., 1998). The cDNAs encoded by GSTM1 and GSTM2 share a remarkable 99% sequence identity (Vorachek et al., 1991). The fact that GSTM1 and GSTM2 are physically linked suggests that the frequent deletion of the GSTM1 locus is caused by unequal crossing-over (Pearson et al., 1993). Furthermore, in HeLa cells, it has been confirmed that GSTM2 overexpression, following transient knockdown of GSTM1 and the absence of GSTM1 activity, may be compensated by the overexpression of GSTM2 (Bhattacharjee et al., 2013). Moreover, existence of linkage disequilibrium between GSTM1 and GSTM3 suggests that association between phenotype and GSTM1 genotypes may also reflect polymorphism in GSTM3 or even other GSTM genes (Wu et al., 2012).