Subribosomal particles and the transport of messenger RNA in HeLa cells

Abstract

Fractionation of HeLa cell cytoplasm on sucrose gradients confirms the presence of subribosomal particles sedimenting at 45 s and 62 s. When cells are exposed for 30 minutes or less to radioactive uridine, the rapidly labeled RNA of the 45 s particle can be distinguished from ribosomal RNA by its sedimentation coefficient and its high efficiency of hybrid formation with homologous DNA. It is suggested that a complex between messenger RNA and the 45 s subribosomal particle may be the first step in the assembly of polysomes, as well as a mechanism for transporting messenger RNA from nucleus to cytoplasm.