A comparative study of the protein components of ribonucleoprotein particles isolated from rat liver and hepatoma nuclei

Abstract

Ribonucleoprotein particles (informofers) were isolated from rat liver nuclei by washing and sonicating the nuclei in 0.14 M NaCl containing 0.001 M MgCl 2 and 0.01 M Tris-HCl, pH 8.0. Sonication released about twice as many particles as were found when the nuclei were washed. Nuclei, isolated from transplantable hepatomas induced by the carcinogen 3′-MeDAB, only released particles during sonication. Particles from liver and hepatoma nuclei were purified on sucrose gradients and solubilized in 1% sodium dodecyl sulphate containing 1% 2-mercapto-ethanol and 8 M urea. Solubilized protein components separated into at least 20 distinct bands in 10% acrylamide gels containing 0.1% sodium dodecyl sulphate and had molecular weights ranging from 17 000 to 185 000. Although gel patterns of tumour and liver ribonucleo-proteins were very similar, a wide variation in the relative amounts of the tumour components was found. The major quantitative difference which was found to be a constant feature of all the tumour patterns studied, was a 60 to 70% decrease in the relative amount of a polypeptide having an apparent molecular weight of about 125 000.