Nuclear localization and DNA binding of the transforming gene product of avian myelocytomatosis virus

Abstract

Oncornaviruses transform cells either directly through a virus-coded oncogene¹ or, if they lack such a gene, indirectly by promoter insertion^2–4 into the cellular genome and activation of a cellular gene. Both transformation mechanisms ultimately result in abnormally high expression of normal genes. Recently, the activated cellular gene in certain lymphomas⁴ has been shown to be homologous to the oncogene of an acute avian leukaemia virus, MC29. In MC29 the oncogene is fused to the viral structural gene, gag. The product of this fused gene is a protein of molecular weight 110,000 (110 K)^5–7, designated p110^gag–myc. We have characterized this protein by using monoclonal antibodies against p19, the N-terminal portion of the gag–myc fusion or 110 K protein and purified it 3,700-fold by immune affinity column chromatography. Immunofluorescence studies and cell fractionation of MC29-transformed fibroblasts indicate that the 110 K protein is predominantly located in the nucleus. Moreover, the purified protein binds to double-stranded DNA. These properties may be related to the role of the protein in transformation.