Molecular biology of the pathogenesis of Sendai viruses.

Protease activation mutant (ts-f1) was isolated from persistently infected cells, and a pantropic mutant, F1-R, was derived from ts-f1. The mutants have been found to be extremely useful for investigations on the molecular biology of paramyxoviruses. The genome of the mutants has been sequenced and mutations were revealed in several proteins encoded by the genes. Three of the six mutations in the fusion (F) proteins were considered prime candidates for the determinants of pantropism. Characterization of the revertants, that are no longer pantropic and derived from F1-R, revealed that the mutation at amino acid residue (115 Arg to Pro) of the F protein is responsible for pantropism. Another important finding was bipolar budding of F1-R in polarized epithelial cells and mouse bronchial epithelium. It has been postulated that mutation(s) in the matrix (M) protein may be associated with bipolar budding since the revertants retained this phenotype of F1-R.