[A change in the relative concentration of individual fractions of low molecular weight nuclear RNA in tumor tissues].

Low molecular weight nuclear RNAs (LMWN RNAs) of normal and neoplastic tissues: the rat liver and Zajdela hepatoma, mouse spleen and NK/Ly ascites tumor, as well as the cultures of normal chick embryo fibroblasts and of those transformed with Rous sarcoma virus were studied by electrophoresis in 8% and 15% polyacrylamide gels. As a result of the study no qualitative differences, i.e. differences in the number of LMWN RNA main fractions and their electrophoretic mobility were found. But there were revealed quantitative variations in the relative amount of definite fractions of these RNAs. An increase of the U3 RNA content in ascites tumors may be connected with an enhancement of the ribosomal RNA synthesis. Variations in the content of low molecular weight RNAs in oncogenic virus transformed cells may reflect an excessive synthesis of low molecular weight viral RNAs during the process of virus reproduction. The quantitative alterations observed seem to be of special value since LMWN RNAs are likely to perform regulatory functions.