Host cell proteins required for measles virus reproduction

Department of Immunology and Medical Microbiology, University of Florida College of Medicine, Gainesville, Florida 32610, U.S.A. We have developed a cell-free system derived from measles virus-infected cells that supported the transcription and replication of measles virus RNA in vitro . The data suggest that tubulin may be required for these reactions, since an anti- -tubulin monoclonal antibody inhibited viral RNA synthesis and the addition of purified tubulin stimulated measles virus RNA synthesis in vitro . Tubulin may be a subunit of the viral RNA polymerase, since two different anti-tubulin antibodies, one specific for the - and another specific for the -subunit of tubulin, coimmunoprecipitated the measles virus L protein as well as tubulin from extracts of measles virus-infected cells. Other experiments further implicated actin in the budding process during virus maturation, as there appeared to be a specific association of actin in vitro only with nucleocapsids that have terminated RNA synthesis, which is presumably a prerequisite to budding. Present address: Department of Microbiology, University of Southern California School of Medicine, Los Angeles, California 90033, U.S.A. Received 7 June 1989; accepted 13 December 1989.