Sequence analysis and regulation of rat liver glutathione S-transferase mRNAs.

We have utilized polysomal immunoadsorption techniques to purify the rat liver glutathione S-transferase mRNAs. Using the purified mRNAs as template, cDNA clones complementary to the Ya, Yb1, and Yc mRNAs have been constructed. The cDNA clones have been utilized in RNA blot hybridization and nuclear run-off assays to demonstrate that the Ya and Yb mRNAs are elevated 8 and 5-fold, respectively by phenobarbital; whereas the Yc mRNA is elevated only 2.0-fold. The elevation in glutathione S-transferase mRNAs is due in part to transcriptional activation of the corresponding genes. Nucleotide sequence analysis of the three glutathione S-transferase clones suggest that the Ya and Yc genes represent one rat liver glutathione S-transferase gene family whereas the Yb genes represent a second distinct glutathione S-transferase gene family. The construction of these cDNA clones will allow identification and characterization of the glutathione S-transferase structural genes as well as aid in the identification of regulatory elements that are responsible for transcriptional activation of the genes by xenobiotics.