A role for the Sendai virus P protein trimer in RNA synthesis.
The SeV P protein is found as a homotrimer (P3) when it is expressed in mammalian cells, and trimerization is mediated by a predicted coiled-coil motif which maps within amino acids (aa) 344 to 411 (the BoxA region). The bacterially expressed protein also appears to be trimeric, apparently precluding a role for phosphorylation in the association of the P monomers. I have examined the role of P trimerization both in the protein's interaction with the nucleocapsid (N:RNA) template and in the protein's function on the template during RNA synthesis. As with the results of earlier experiments (32), I found that both the BoxA and BoxC (aa 479 to 568) regions were required for stable binding of P to the N:RNA. Binding was also observed with P proteins containing less than three BoxC regions, suggesting that trimerization may be required to permit contacts between multiple BoxC regions and the N:RNA. However, these heterologous trimers failed to function in viral RNA synthesis, indicating that the third C-terminal leg of the trimer plays an essential role in P function on the template. We speculate that this function may involve the movement of P (and possibly the polymerase complex) on the template and the maintenance of processivity.
Curran
J
J
Department of Genetics and Microbiology, University of Geneva Medical School, Switzerland. curran@cmu.unige.ch
D006367:HeLa Cells; D006801:Humans; D019590:Nucleocapsid Proteins; D009698:Nucleoproteins; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D012367:RNA, Viral / Q000096:biosynthesis*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D018108:Respirovirus / Q000235:genetics* / Q000502:physiology; D014407:Tumor Cells, Cultured; D014758:Viral Core Proteins / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*
D019590:Nucleocapsid Proteins; D009698:Nucleoproteins; C055859:P protein, Sendai virus; D010750:Phosphoproteins; D012367:RNA, Viral; D011993:Recombinant Fusion Proteins; D014758:Viral Core Proteins; D014764:Viral Proteins