A comparison of polysomal messenger ribonucleoprotein particles from normal and neoplastic rat liver.

Free polysomes were isolated from normal and regenerating rat liver and from Morris hepatomas 7777, 7800, 5123C and 9618A. Sucrose gradient analysis ruled out the possibility of any significant messenger RNA degradation in these polysome preparations. The ethylenediaminetetraacetate-disrupted polysomes were fractionated on oligodeoxythymidylic acid-cellulose columns. The column-bound polyriboadenylic acid-containing messenger ribonucleoprotein particles were eluted with a formamide buffer, precipitated with ethanol, and subjected to polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The messenger RNA-associated proteins from the different tissues were qualitatively similar, but two proteins with molecular weights of 66,000 and 109,000 found as minor proteins in normal liver appeared on gels as major protein bands when hepatoma messenger ribonucleoprotein particles were examined. The 66,000- and 109,000-molecular-weight proteins in these particles from regenerating liver appeared quantitatively similar to those isolated from normal liver.