The matrix protein of vesicular stomatitis virus inhibits nucleocytoplasmic transport when it is in the nucleus and associated with nuclear pore complexes

The matrix (M) protein of vesicular stomatitis virus (VSV) is a potent inhi bitor of bidirectional nuclear transport. Here we demonstrate that inhibiti on occurs when M protein is in the nucleus of Xenopus laevis oocytes and th at M activity is readily reversed by a monoclonal antibody (alphaM). We ide ntify a region of M protein, amino acids 51 to 59, that is required both fo r inhibition of transport and for efficient recognition by alphaM. When exp ressed in transfected HeLa cells, M protein colocalizes with nuclear pore c omplexes (NPCs) at the nuclear rim. Moreover, mutation of a single amino ac id, methionine 51, eliminates both transport inhibition and targeting to NP Cs. We propose that M protein inhibits bidirectional transport by interacti ng with a component of the NPC or an NPC-associated factor that participate s in nucleocytoplasmic transport.