Animal DNA‐Dependent RNA Polymerases

Abstract

This paper describes a method for the purification of calf thymus DNA‐dependent RNA polymerase B activity and its subsequent resolution into two enzymes, BI and BII. The method of purification of the combined B activities involved chromatography on phosphocellulose and hydroxyapatite and centrifugation through a glycerol density gradient. Enzymes BI and BII were separated by two successive chromatographic steps on DEAE‐cellulose. Addition of 30% glycerol to all buffers increased the stability of the enzymes throughout the purification. The polymerases were over 95% pure and free of contaminating nucleases. It seems unlikely that enzyme BII could derive from enzyme BI by a specific proteolytic process occurring during purification of the B activity.