THE NONSTRUCTURAL-C PROTEIN IS NOT ESSENTIAL FOR MULTIPLICATION OF EDMONSTON-B STRAIN MEASLES-VIRUS IN CULTURED-CELLS

Measles virus (MV) is a highly contagious agent which causes a major h ealth problem in developing countries. Efficacious and safe live atten uated vaccine strains are available, but for the elimination of measle s a better knowledge about the molecular biology of MV appears crucial . Whereas the roles of the six structural proteins in the replication cycle are known, the functions of the two nonstructural proteins C and V are unclear, which is also true for related viruses. In vitro studi es implicating Sendai virus suggest that the C protein might be involv ed in downregulating viral mRNA synthesis (J. Curran, J. B. Marq, and D. Kolakofsky, Virology 189, 647-656, 1992). However, not all members of the Paramyxovirinae subfamily encode this protein, raising the ques tion about its importance for the viral replication cycle. Taking adva ntage of a recently developed reverse genetics system allowing MV reco very from cloned DNA (F. Radecke, P. Spielhofer, H. Schneider, K. Kael in, M. Huber, C. Dotsch, G. Christiansen, and M. A. Billeter, EMBO J. 14, 5773-5784, 1995), the question was addressed whether the C protein is essential for the life cycle of MV. A plasmid was constructed to p roduce a derivative of the Edmonston B vaccine strain, MV C- EdB, havi ng its C reading frame silenced by two point mutations. The C- mutant MV could indeed be rescued, and it multiplies in cultured cells withou t obvious impairment. (C) 1996 Academic Press, Inc.