IDENTIFICATION OF CLASS-MU GLUTATHIONE TRANSFERASE GENES GSTM1-GSTM5 ON HUMAN CHROMOSOME-1P13

The GSTM1, GSTM2, GSTM3, GSTM4, and GSTM5 glutathione transferase gene s have been mapped to human chromosome 1 by using locus-specific PCR p rimer pairs spanning exon 6, intron,6, and exon 7, as probes on DNA fr om human/hamster somatic cell hybrids. For GSTM1, the assignment was c onfirmed by Southern blot hybridization to a pair of 12.5/2.4-kb HindI II fragments. The GSTM1-specific primer pairs can be used to identify individuals carrying non-null GSTM1 alleles. The organization of these five genes was confirmed by the isolation of a yeast artificial chrom osome clone (GSTM-YAC2) that contains all five genes. With this clone, the location of the GSTM1-GSTM5 gene cluster on chromosome 1 was conf irmed by fluorescence in situ hybridization. Both regional assignment using the fractional length method and examination of probe signal wit h reference to R-banded chromosomes induced by BrdU places the gene cl uster in or near the 1p13.3 region. The close physical proximity of th e GSTM1 and GSTM2 loci, which share 99% nucleotide sequence identity o ver 460 nucleotides of 3'-untranslated mRNA, suggests that the GSTM1-n ull allele may result from unequal crossing-over.