| Summary |
Newcastle disease virus, a major pathogen of poultry, is a member of the Paramyxoviridae family of viruses. Paramyxoviruses infect a broad spectrum of hosts including humans. Upon attachment and penetration of a suitable host cell these negative strand RNA viruses must first independently transcribe their genome using a virion associated RNA polymerase and independently translate their viral proteins before replication of the genome can occur. Transcription of the viral mRNA's has been shown to be carried out on the nucleocapsid by the viral transcriptase which consists of the viral polymerase (L) and the virus encoded phosphoprotein (P). Both of these proteins, in conjunction with the nucleocapsid protein (NP), are responsible for complete replication of the negative strand genome. Due to the P protein's participation in both the transcriptase and the replicase activities as well as serving as a chaperone for unbound NP during replication, it was of interest to determine what effect over-expression of the NDV P protein would have on viral replication. A cDNA copy of the Newcastle disease virus phosphoprotein from the Beaudette C strain was inserted into the eucaryotic expression vector pRc/RSV. The resulting clone, pRc/RSV-P, was transiently transfected into CHO-Kl cells. These cells were subsequently infected with NDV or vesicular stomatitis virus (VSV). Viral titers from infected CHO cells expressing P protein had no significant difference from infected control CHO cells (CHO cells transfected with pRc/RSV). The level of NDV viral proteins between NDV infected CHO cells transfected with pRc/RSV-P and pRc/RSV, as detected by immunoblotting, indicated a 58-68% higher level of viral protein synthesis in those cells transfected with the P gene cDNA sequences. It is yet to be determined if the enhancement ofprotein synthesis is a result of the phosphoprotein acting at the level of mRNA transcription or translation. |
