Presence of actin in oncornaviruses.

A 43K protein present in avian myeloblastosis virus has been identified as actin by 2D gel electrophoresis and peptide mapping proteolysis. Electron microscopy of chicken embryo fibroblasts infected with different pseudotypes of oncornaviruses treated with anti-actin antibody showed positive staining at the level of the virions especially on buds. Our results indicate that this actin is unlikely to have been artefactually absorbed at the virion surface during its preparation. It may therefore play a possible role in the budding of enveloped virions.