Evidence for coupled synthesis of mRNA for ribosomal proteins and rRNA.

Two-dimensional gel electrophoresis revealed quantitative differences in the 35S-methionine labeled proteins synthesized in vitro in the wheat germ system containing poly A(+) mRNA of normal liver, regenerating liver or Novikoff hepatoma cells. A group of low molecular weight proteins which comigrated with proteins of 40S ribosomal subunits were synthesized in a much greater concentration with the poly A(+) mRNA from the latter two sources. This correlates with increased synthesis of ribosomal proteins in regenerating liver or tumors which is temporally coupled with the increased nucleolar synthesis of rRNA precursors.