Two regions of the P protein are required to be active with the L protein for human parainfluenza virus type 1 RNA polymerase activity

The para myxovirus P protein is an essential component of the viral RNA pol ymerase composed of P and L proteins. In this study, we characterized the p hysical and functional interactions between P and L proteins using human pa rainfluenza virus type 1 (hPIV1) and its counterpart Sendai virus (SV). The hPIV1 P and SV L proteins or the SV P and hPIV1 L proteins formed complexe s detected by anti-P antibodies. Functional analysis using the minigenome S V RNA containing CAT gene indicated that the hPIV1 P-SV L complex, but not the SV P-hPIV1 L complex, was biologically active. Mutant SV P or hPIV1 P c DNAs, which do not express C proteins, showed the same phenotype with wild- type P cDNAs, indicating that C proteins are not responsible for the dysfun ction of SV P-hPIV1 L polymerase complex. Using the chimeric hPIV1/SV P cDN As, we identified two regions (residues 387-423 and 511-568) on P protein, which are required for the functional interaction with hPIV1 L. These regio ns overlap with a previously identified domain for oligomer formation and b inding to nucleocapsids. Our results indicate that in addition to a P-L bin ding domain, hPIV1 L requires a specific region on P protein to be biologic ally functional as a polymerase, (C) 2001 Academic Press.