Nonhistone protein BA is a glutathione S-transferase localized to interchromatinic regions of the cell nucleus

J Cell Biol. 1986 Feb;102(2):600-9. doi: 10.1083/jcb.102.2.600.

Abstract

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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acids / analysis
  • Animals
  • Cell Compartmentation
  • Cell Nucleus / enzymology*
  • Cell Nucleus / ultrastructure
  • Chromosomal Proteins, Non-Histone / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Fluorescent Antibody Technique
  • Glutathione Transferase / analysis
  • Glutathione Transferase / metabolism*
  • Immunoenzyme Techniques
  • Macromolecular Substances
  • Microscopy, Electron
  • Molecular Weight
  • Peptide Fragments / analysis
  • Rats
  • Ribonucleoproteins / metabolism
  • Ribonucleoproteins, Small Nuclear

Substances

  • Amino Acids
  • Chromosomal Proteins, Non-Histone
  • Macromolecular Substances
  • Peptide Fragments
  • Ribonucleoproteins
  • Ribonucleoproteins, Small Nuclear
  • Glutathione Transferase