INTERACTION BETWEEN NUCLEOCAPSID PROTEIN (NP) AND PHOSPHOPROTEIN (P) OF HUMAN PARAINFLUENZA VIRUS TYPE-2 - ONE OF THE 2 NP BINDING-SITES ONP IS ESSENTIAL FOR GRANULE FORMATION

The paramyxovirus phospho- (P) and nucleocapsid (NP) proteins are invo lved in transcription and replication of the viral genome, To study th e interaction between NP and P proteins, we established HeLa cell line s that constitutively expressed the NP and/or P proteins of human para influenza virus type 2 (hPIV-2), Co-immunoprecipitation assays reveale d that the NP and P proteins can form complexes in HeLa cells expressi ng both proteins (HeLa-NP+P cells) and in mixed cell lysates of HeLa-N P and HeLa-P cells, Deletion mutant analysis of the P protein was perf ormed to identify the regions of P protein that interact with NP prote in. The results indicate that two independent NP-binding sites exist o n P protein: one is located in the N-terminal part of the protein, aa 1-47, and the other in the C-terminal part, aa 357-395, In addition, c ells co-expressing NP and P proteins with N-terminal deletions showed immunofluorescence staining patterns (granular pattern) similar to tho se found in hPIV-2-infected cells, However, cells coexpressing NP and P proteins with C-terminal deletions showed a different immunofluoresc ence staining pattern (diffuse pattern), indicating that the C-termina l region is required for granule formation.