A distinct RNA polymerase activity, synthesizing 5.5 s, 5 s and 4 s RNA in nuclei from adenovirus 2-infected HeLa cells

Abstract

A distinct RNA polymerase activity which synthesizes low molecular-weight RNA has been identified in the nuclei of HeLa cells. The products of the polymerase activity are RNA molecules of discrete size. In nuclei from adenovirus 2-infected cells, RNA, which co-migrates in gel electrophoresis with host cell 5 s RNA and 5.5 s virus-associated RNA, is labeled. The activity also labels RNA with the properties of precursor to transfer RNA. The kinetics of labeling and the results of chase experiments suggest that the polymerase activity is initiating the synthesis of new molecules. Consistent with this hypothesis is the observation that the 5.5 s virus-associated RNA molecules contain radioactive pppGp and uridine, which are presumed to arrive from the 5′- and 3′-ends, respectively. The polymerase activity is completely insensitive to inhibition by α-amanitine, and it is comparatively active when Mn 2+ is substituted for Mg 2+. These properties are in contrast to those of the polymerase activity transcribing high molecular-weight heterogeneous RNA from either the host cell or the adenovirus genome. Thus, it appears that the adenovirus genome is transcribed by two distinct polymerase activities: one resembles closely the host cell polymerase transcribing high molecular-weight RNA, and the other is similar to the host cell activity forming low molecular-weight RNA species.