Proteins bound to heterogeneous nuclear RNA of simian-virus-40-infected cells

Heterogeneous nuclear RNA . protein (hnRNA . protein) complexes from simian-virus-40 (SV40)-infected cells late in infection contain 7--10% RNA sequences specific to SV40 DNA. The SV40 nuclear RNA . protein complexes sediment at 60--70 S. The reality and specificity of the RNA-protein association is shown in metrizamide gradients. Protein and RNA lebels of hnRNA . protein-particles in SV40-infected cells follow a parallel pattern with a peak at 1.28 g/cm2 whereas a mixture of ribosomal RNA and soluble cytoplasmic proteins is separated according to the different densities in metrizamide. Analysis of hnRNA . protein from infected cells by two-dimensional gel electrophoresis shows the presence of a number of new proteins. It is demonstrated that three of these proteins are cellular ones induced by the virus infection and hence constitute good candidates to be specific RNA . protein particles for virus nuclear RNA. The presence of actin in hnRNA . protein particles from normal and SV40-infected cells and the presence of the major capsid protein VP1 in hnRNA . protein particles from SV40-infected cells is discussed.