The N-terminal conserved domain of rubella virus capsid interacts with the C-terminal region of cellular p32 and overexpression of p32 enhances the viral infectivity.

Cellular 'defense collagens' are produced to launch virus-specific responses to clear the invading viruses. Cellular p32, the C1q binding protein is one such protein. In this report, we identified the interaction of p32 derived from a human lung diploid cell line (WI-38) with rubella virus capsid (RVCP from Therien strain) N-terminal 28-amino acid domain, which is conserved among several RV strains including the vaccine strains. We further identified that the C-terminal 69 aa of the mature p32 is sufficient to interact with the CP. In addition, we observed that in three independent Vero 76-derived cell lines constitutively overexpressing p32, the RV infectivity was enhanced. Our results suggest that RV has evolved a strategy whereby one of its proteins is recruited to interact with, and exploit the cellular defense machinery to its advantage.