Use of electron microscopic and immunogold labeling techniques to determine polyomavirus recombinant VP1 capsid-like particles entry into mouse 3T6 cell nucleus

Murine polyomavirus major structural protein VP1 could assemble into capsid-like particles when expressed in the baculovirus system. The recombinant capsid-like particles that were purified by CsCl density gradient centrifugation were capable of packaging host DNA. Electron microscopic and immunogold labeling techniques were used to study the entry of these VP1 recombinant capsid-like particles into mouse 3T6 cells. It was found that these VP1 recombinant capsid-like particles, which lack polyomavirus minor structural proteins (VP2 and VP3), use the same mechanism to enter mouse 3T6 cell cytoplasm and nucleus as that used by native polyomavirus virions.