Vesicular stomatitis virus M protein in the nuclei of infected cells

The M protein of vesicular stomatitis virus (VSV) was localized in the nuclei and cytoplasm of VSV-infected cells by subcellular fractionation and immunofluorescence microscopy. Nuclei isolated from VSV-infected Friend erythroleukemia cells were fractionated into a nuclear membrane and a nucleoplasm fraction by DNase digestion and differential centrifugation. G protein was present in the membrane fraction, and M protein was present in the nucleoplasm fraction. Immunofluorescence detection of M protein in the nucleus required that fixed cells be permeabilized with higher concentrations of detergent than were required for detection of M protein in the cytoplasm of VSV-infected BHK cells.