Increased phosphorylation of a liver ribosomal protein in mice carrying ascites tumours.

The extent of phosphorylation of ribosomal protein S6 in the livers of mice carrying the Krebs II ascites tumour has been examined by two-dimensional gel electrophoresis. Seven days after injection, an increase was observed in the amount of stained material migrating at the position of the phosphorylated derivatives of ribosomal protein S6, and there was also an increase in the proportion of ribosomes sedimenting as monosomes. The extent of phosphorylation of ribosomal protein S6 in the ascites cells themselves was low. The findings are discussed in relation to the phosphorylation of ribosomal protein S6 in transformed cells and in other pathological states of the liver.