The leader RNA of vesicular stomatitis virus is bound by a cellular protein reactive with anti-La lupus antibodies.

The leader RNA transcript of vesicular stomatitis virus (VSV) has been immunoprecipitated from infected BHK cell extracts by anti-La specific sera from patients with systemic lupus erythematosus (SLE). This association was specific as lupus anti-sera with other specificities failed to precipitate leader RNA. The amount of leader RNA associated with the La antigen peaked 4 hr post infection and then declined. Leader RNA complexed with viral nucleocapsid proteins increased at a slower rate but eventually predominated 6 hr post infection. By 16 hr all of the leader RNA was associated with nucleocapsid proteins. Although a significant portion of the leader RNA was present in isolated nuclei 4 hr post infection, all of the leader RNA outside the nucleus was bound to La protein. Leader RNA is the first non-RNA polymerase III product found to associate with the La protein. The proposed function of the leader-La complex in VSV transcription and replication and in viral cytopathology is discussed.