Virus multiplication and induction of apoptosis by Sendai virus: role of the C proteins

Sendai virus (SeV) P gene encodes a nested set of carboxyl-coterminal proteins (C', C, Y1 and Y2), which are referred to collectively as the C proteins. Characterization of the virus multiplication and cellular responses in HEp-2 cells infected with the recombinant SeV which lacks two (C' and C), three (C', C and Y1) or all the four C proteins revealed that all the recombinant viruses can grow in the cells to various extents, depending, apparently, on the number of species expressing C protein. In reverse proportion to the viral growth ability, these viruses induced apoptosis in the infected cells. These results indicate that Y2 protein has an antiapoptotic activity, and suggest that this activity works in an additive manner with the longer C protein(s) (C' and/or C) of SeV in order to suppress virus-induced apoptosis in the SeV-infected cells. Apparently, the antiapoptotic activity of the C proteins supports virus multiplication in the infected cells.