Fractionation of RNA polymerase subspecies from soybean hypocotyls by isoelectric focusing in Sephadex

RNA polymerase enzymes isolated from chromatin of 6-day-old soybean hypocotyls are resolved into two major and one minor species of activity by DEAE-Sephadex chromatography. A soluble form of the enzyme, isolated from the postchromatin supernatant fraction, shows a broad peak of activity when fractionated by this method. The elution characteristics and α-amanitin sensitivity data indicate the two major chromatin-bound activities to be Class I and III enzymes, while the minor chromatin-bound activity and the soluble enzyme are representative of the Class II enzymes. In contrast to these profiles, fractionation of these enzyme preparations by the new method of isoelectric focusing in Sephadex G-15 yields five distinct chromatin-bound and four soluble subspecies. The relationships of these observed activities to their parent DEAE classes are investigated, showing two subspecies within the Class I and III RNA polymerase enzymes, respectively, and four subspecies within the Class II enzymes.