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. 2011 Dec 27;6(12):e29366. doi: 10.1371/journal.pone.0029366

Figure 1. Deletion polymorphisms of the GSTT1 and GSTT2B genes.

Figure 1

The GSTT1 and GSTT2 genes are part of the Theta-class GST gene cluster on chromosome 22q11.23. GSTT1 and GSTT2 are separated by approximately 50 kb and share 55% sequence homology. GSTT1 is flanked by two 18 kb regions, HA5 and HA3, which are more than 90% homologous. In their central portion, HA3 and HA5 share a 403-bp sequence with 100% identity. HA5 and HA3 are direct repeats. The GSTT1 null allele arises by homologous recombination of the left and right 403-bp repeats, which results in a 54-kb deletion containing the entire GSTT1 gene. GSTT2 is positioned adjacent to the HA5 repeat. The duplicate copy of GSTT2 is a pseudogene named GSTT2B, because of an abnormal exon 2/intron 2 splice site that causes a premature translation stop. GSTT2 and GSTT2B are inverted repeats. The deletion of GSTT2B has a strong influence on GSTT2 gene expression, as described in the text.