Vesicular stomatitis virus phosphoprotein dimerization domain is dispensable for virus growth

International audienceThe phosphoprotein of the nonsegmented negative-sense RNA viruses is a multimeric modular protein that is essential for RNA transcription and replication. Despite a great variability in length and sequence, the architecture of this protein is conserved among the different viral families, with a long N-terminal intrinsically disordered region comprising a nucleoprotein chaperone module, a central multimerization domain (PMD), connected by a disordered linker to a C-terminal nucleocapsid-binding domain. The P protein of vesicular stomatitis virus (VSV) forms dimers, and here we investigate the importance of its dimerization domain, PMD, for viral gene expression and virus growth. A truncated P protein lacking the central dimerization domain (PΔMD) loses its ability to form dimer both in vitro and in yeast two-hybrid system but conserves its ability to bind N. In a minireplicon system, the truncated monomeric protein performs almost as well as the full-length dimeric protein, while a recombinant virus harboring the same truncation in the P protein has been rescued and follows similar replication kinetics than the wild-type virus, showing that the dimerization domain of P is dispensable for viral gene expression and virus replication in cell cultures. Because RNA viruses have high mutation rates, it is unlikely that a structured domain such as VSV dimerization domain would persist in the absence of function, but our work indicates that it is not required for the functioning of the RNA polymerase machinery or for the assembly of new viruses.IMPORTANCE The phosphoprotein (P) is an essential and conserved component of all nonsegmented negative-sense RNA viruses, which includes some major human pathogens (rabies, measles, RSV, Ebola or Nipah viruses). P is a modular protein with intrinsically disordered regions and folded domains that plays specific and similar roles in the replication of the different viruses, and in some cases, hijacks cell components to the virus advantage and is involved in immune evasion. All P proteins are multimeric, but the role of this multimerization is still unclear. Here, we demonstrate that the dimerization domain of VSV P is dispensable for the expression of virally encoded proteins and for virus growth in cell cultures. This provides new insights and raises questions about the functioning of the RNA synthesizing machine of the nonsegmented negative-sense RNA viruses