A Factor from Calf Thymus Stimulating DNA-Dependent RNA Polymerase Isolated from this Tissue

Abstract

A large scale purification procedure of RNA polymerase from calf thymus is described. A factor stimulating synthesis of RNA by this enzyme has been extracted from the same tissue. Addition of the factor to the enzyme assay results in a 10-fold increased enzyme activity. This effect is only seen when native and not when denatured DNA is used as template. Several lines of evidence exclude trivial explanations of the stimulation effect and indicate a direct action of the factor on the enzyme. The active agent is probably a protein with a sedimentation constant of about 3 S.