Identification and Characterization of Two Distinctive RNA Binding Activities in Pea Nuclear Extracts

We have identified and purified two RNA binding factors from pea nuclear extracts. One factor (RBF-1) consisted of at least two polypeptides with molecular weights of approximately 27 and 59 kD; each of these polypeptides could be crosslinked to labelled RNA by ultraviolet light. The other factor (RBF-2) also consisted of two polypeptides (of approximately 93 and 126 kD in size) that could be crosslinked to RNA by UV. Both factors showed general preferences for single stranded RNA. However, RBF-1 displayed a preference for poly(A) and poly(U) over poly(G) or poly(C), while RBF-2 had a strong preference for poly(U) over the other three homopolymers. These properties are suggestive of possible roles for these factors in RNA metabolism in plant nuclei.