CHARACTERIZATION OF A NOVEL PLANT POLY(A) POLYMERASE

We have purified and characterized poly(A) polymerases (PAPs) from Pis um sativum, Brassica juncea, and Zea mays. Through chromatography on D EAE-Sepharose and heparin-Sepharose, these PAPs copurified as a single enzyme along with RNPs that could provide RNA substrates for the enzy me. More extensive purification by chromatography on MonoQ resulted in the resolution of the PAPs into as many as three fractions. One of th ese (PAP-I) contained a 43-kDa polypeptide immunologically related to the yeast PAP, and two others (PAP-II and PAP-III) contained RNAs that could serve as substrates for polyadenylation. These fractions by the mselves possessed little PAP activity, but mixtures containing combina tions of these displayed substantial activity. Similar PAP factors (PA P-I and PAP-III) were identified after fractionation of extracts prepa red from Brassica juncea and Zea mays. The factors from one plant were completely interchangeable with those from different plants. We concl ude that the poly(A) polymerases present in vegetative plant tissues c onsist of more than one component. In this respect, they are substanti ally different from other reported plant, mammalian, and yeast PAPs.