The effect of trypsin digestion and ionic strength on RNA polymerase of rat liver

RNA polymerase of rat liver nuclei was assayed at low and at high ionic strength following incubation of the nuclei with trypsin. Digestion with trypsin, to remove histone, stimulated RNA polymerase activity when this was assayed at low ionic strength, but not when RNA synthesis had already been stimulated by the presence of a high salt concentration. Stimulation of RNA polymerase by high ionic strength increased the time during which RNA synthesis was observed. The optimal concentration of divalent cations (Mg⁺⁺ or Mn⁺⁺), which are required for incorporation, was changed by the presence of a high salt concentration. After trypsin treatment, however, nuclei assayed at low ionic strength showed characteristics similar to those of nuclei assayed at high ionic strength, but the incorporation by such nuclei was less than that of nuclei stimulated by high ionic strength.