Solubilized DNA-dependent RNA polymerase activities in resting and growing fibroblast

Abstract

The activities of RNA polymerases I and II were measured in 3T6 [mouse fibroblasts] during the transition from the resting to growing state by solubilization of the enzymes followed by chromatography on DEAE-Sephadex columns. The activity of RNA polymerase II remains unchanged during the first 12 h after serum stimulation while the activity of RNA polymerase I increases and closely parallels the increased activity seen in isolated nuclei. Compared to enzyme from resting cells, RNA polymerase I from serum stimulated cells elutes at a lower ammonium sulfate concentration on DEAE-Sephadex chromatography and its activity shows distinctly different dependencies on the concentration of ammonium sulfate and Mg2+. These observations are discussed in relation to the possible mechanism by which 3T6 regulates the synthesis of preribosomal RNA.