Interaction Of Human Parainfluenza Virus Type 3internal Viral Protein

Human parainfluenza virus type 3(HPIV3)is a nonsegmented,negative-sense,single-stranded RNA virus that belongs to the Paramyxoviridaefamily and can cause lower respiratory tract infections in infants and young children as well as elderly or immunocompromised individuals.However,no effective vaccine has been developed or licensed.The HPIV3 genome consists of 6 open reading frames that encode 6structural proteins:the nucleoprotein(N),phosphoprotein(P),polymerase(L),matrix protein(M),and two glycoproteins,hemagglutinin/neuraminidase(HN)and the fusion protein(F).N,P,and L encapsulate the viral RNA to form a helical assembly termed the ribonucleoprotein(RNP)complex,which is the minimum structure required for viral transcription and replication,The M protein binds directly to the viral envelope and involve for virion assembly.HPIV3 M protein expressed alone is sufficient to assemble and release virus-like particles(VLPs),Virus-like particles have a structure similar to that of virions,except that they contain no viral RNA and are therefore not infectious,so researchers can use virus-like particles to study the assembly and budding of virions.On this basis,it is very feasible to use VLP to study the assembly mechanism of N protein and P protein into virions,and it is also very meaningful to reveal the assembly mechanism of internal viral protein and provide new antiviral treatment strategies This paper show that the M with the L305A point mutation in the M protein(M_L305A)has a VLP formation ability similar to that of wild-type M protein.In addition,recombinant HPIV3(r HPIV3)containing the M_L305Amutation(r HPIV3-M_L305A)could be successfully recovered.And the titer of recombinant HPIV3(r HPIV3)containing the M_L305Amutation(r HPIV3-M_L305A)was at least 10-fold lower than the titer of r HPIV3.Using VLP assembly and co-immunoprecipitation assays,we found that VLPs expressing the M protein(M-VLPs)can efficiently incorporate N and P via an N-M or P-M in-teraction and M_L305A-VLPs had an ability to incorporate P via a P-M interaction similar to that of M-VLPs but were unable to incorporate N and no longer interacted with N.Furthermore,we found that the incorporation of P into M_L305A-VLPs but not M-VLPs was inhibited in the presence of N.In addition,we provide evidence that the C-terminal region of P is involved in its interaction with both N and M and N binding to the C-terminal region of P inhibits the incorporation of P into M_L305A-VLPs.This paper provides new molecular details to support the idea that the N-M interaction and not the P-M interaction is critical for packaging N and P into infectious viral particles.