Nonhistone protein BA is a glutathione S-transferase localized to interchromatinic regions of the cell nucleus.
A DNA-binding nonhistone protein, protein BA, was previously demonstrated to co-localize with U-snRNPs within discrete nuclear domains (Bennett, F. C., and L. C. Yeoman, 1985, Exp. Cell Res., 157:379-386). To further define the association of protein BA and U-snRNPs within these discrete nuclear domains, cells were fractionated in situ and the localization of the antigens determined by double-labeled immunofluorescence. Protein BA was extracted from the nucleus with the 2.0 M NaCl soluble chromatin fraction, while U-snRNPs were only partially extracted from the 2.0 M NaCl-resistant nuclear structures. U-snRNPs were extracted from the residual nuclear material by combined DNase I/RNase A digestions. Using an indirect immunoperoxidase technique and electron microscopy, protein BA was localized to interchromatinic regions of the cell nucleus. Protein BA was noted to share a number of chemical and physical properties with a family of cytoplasmic enzymes, the glutathione S-transferases. Comparison of the published amino acid composition of protein BA and glutathione S-transferases showed marked similarities. Nonhistone protein BA isolated from saline-EDTA nuclear extracts exhibited glutathione S-transferase activity with a variety of substrates. Substrate specificity and subunit analysis by SDS polyacrylamide gel electrophoresis revealed that it was a mixture of several glutathione S-transferase isoenzymes. Protein BA isolated from rat liver chromatin was shown by immunoblotting and peptide mapping techniques to be two glutathione S-transferase isoenzymes composed of the Yb and Yb' subunits. Glutathione S-transferase Yb subunits were demonstrated to be both nuclear and cytoplasmic proteins by indirect immunolocalization on rat liver cryosections. The identification of protein BA as glutathione S-transferase suggests that this family of multifunctional enzymes may play an important role in those nuclear domains containing U-snRNPs.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000201:enzymology* / Q000648:ultrastructure; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D005982:Glutathione Transferase / Q000032:analysis / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D051381:Rats; D012261:Ribonucleoproteins / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear
D000596:Amino Acids; D002868:Chromosomal Proteins, Non-Histone; D046911:Macromolecular Substances; D010446:Peptide Fragments; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear; D005982:Glutathione Transferase