Simian virus 40 large tumor antigei (electrofocusing/messenger ribonucleoprotein/phosphoprotein/regu

Simian virus 40 large tumor antigen was isolated by immunoaffinity chromatography from monkey or mouse cell cultures undergoing lytic or transforming infection. RNase-treated gel-purified large tumor antigen, on hydrolysis with alkali, gave about equimolar amounts of AMP, GMP, CMP, and UMP. Fur- thermore, RNA fragments of =45 nucleotides could be isolated from large tumor antigen purified by the same procedure. Map- ping of the T1 oligonucleotides showed a high complexity, as in- dicated by the presence of unique sequences of 15-30 nucleotides and of poly(A). This is compatible with the hypothesis that these RNA fragments are derived from cellular pre-mRNAs or mRNAs. Our results suggest that Simian virus 40 large tumor antigen is a RNA-binding protein and might possibly be involved in regulation of synthesis, maturation, or translation of cellular mRNAs.