Recombinant Porcine reproductive and respiratory syndrome virus Replicase polyprotein 1ab (rep), partial

The replicase polyprotein 1ab is a multifunctional protein: it contains the activities necessary for the transcription of negative stranded RNA, leader RNA, subgenomic mRNAs and progeny virion RNA as well as proteinases responsible for the cleavage of the polyprotein into functional products.; Nsp1 is essential for viral subgenomic mRNA synthesis.; Nsp1-alpha inhibits IFN-beta production. Counteracts the action of NF-kappaB by decreasing the phosphorylation of IkappaB-alpha, such that the degradation of IkappaB-alpha is suppressed. This leads to the blockage of NF-kappaB nuclear translocation and thus interference of NF-kappaB activation. Also seems to inhibit IRF3-dependent pathways.; Nsp2 cysteine proteinase which cleaves the nsp2/nsp3 site in the polyprotein. Also displays deubiquitinating and deISGylase activities. The deubiquitinating activity cleaves both ubiquitinated and ISGylated products and may therefore regulate ubiquitin and ISG15 dependent host innate immunity. Deubiquitinates host NFKBIA, thereby interfering with NFKBIA degradation and impairing subsequent NF-kappa-B activation.; The 3C-like serine proteinase chain is responsible for the majority of cleavages as it cleaves the C-terminus of the polyprotein.; The helicase chain, which contains a zinc finger structure, displays RNA and DNA duplex-unwinding activities with 5' to 3' polarity.; Plays a role in viral transcription/replication and prevents the simultaneous activation of host cell dsRNA sensors, such as MDA5/IFIH1, OAS, and PKR. Acts by degrading the 5'-polyuridines generated during replication of the poly(A) region of viral genomic and subgenomic RNAs. Catalyzes a two-step reaction in which a 2'3'-cyclic phosphate (2'3'-cP) is first generated by 2'-O transesterification, which is then hydrolyzed to a 3'-phosphate (3'-P). If not degraded, poly(U) RNA would hybridize with poly(A) RNA tails and activate host dsRNA sensors.