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. Inhibits host IFN-beta production. Plays a role in the degradation of the host transcriptional activator CREBBP protein. The degradation of host CREBBP which is a key component of the IFN enhanceosome is likely responsible for the inhibition of interferon mediated by Nsp1-alpha. Participates also in the inhibition of host NF-kappa-B activation by counteracting LUBAC-dependent induction of NF-kappa-B. Reduces host NEMO ubiquitination by blocking the interaction between the two LUBAC complex components RNF31 and SHARPIN. Plays a role in blocking host mRNA nuclear export to the cytoplasm and subversion of host protein synthesis. Additionally, inhibits the interferon-activated JAK/STAT signal transduction by mediating the ubiquitination and subsequent proteasomal degradation of host KPNA1. Multifunctional protein that acts as a viral protease and as a viral antagonist of host immune response. Cleaves the nsp2/nsp3 site in the viral polyprotein. Displays deubiquitinating activity that cleaves both ubiquitinated and ISGylated products and therefore inhibits ubiquitin and ISG15-dependent host innate immunity. Deubiquitinates also host NFKBIA, thereby interfering with NFKBIA degradation and impairing subsequent NF-kappa-B activation. Plays a role in the inhibition of the immune response by interacting with host IFITM1. This interaction leads to the proteasomal degradation of the IFN-induced antiviral protein IFITM1. Cleaves the majority of cleavage sites present in the C-terminus of the polyprotein. Triggers host apoptosis through caspase-3, -8, and -9 activations. Subverts host innate immune responses through its protease activity. Targets the NF-kappa-B essential modulator NEMO and mediates its cleavage. Blocks host interferon beta induction and downstream signaling by cleaving mitochondrial MAVS, dislodging it from the mitochondria. Impairs host defense by cleaving host mRNA-decapping enzyme DCP1A to attenuate its antiviral activity. Plays a role in the initial induction of autophagosomes from host reticulum endoplasmic. Plays a role in the inhibition of host STAT3 signaling pathway by inducing the degradation of STAT3. Responsible for replication and transcription of the viral RNA genome. 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 (By similarity). 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) (By similarity). If not degraded, poly(U) RNA would hybridize with poly(A) RNA tails and activate host dsRNA sensors (By similarity). a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) ATP + H2O = ADP + H(+) + phosphate ATP + H2O = ADP + H(+) + phosphate Thiol-dependent hydrolysis of ester, thioester, amide, peptide and isopeptide bonds formed by the C-terminal Gly of ubiquitin (a 76-residue protein attached to proteins as an intracellular targeting signal). uridylyl-uridylyl-ribonucleotide-RNA = a 3'-end uridylyl-2',3'-cyclophospho-uridine-RNA + a 5'-end dephospho-ribonucleoside-RNA Nsp1-alpha papain-like: Interacts with host RNF31. Interacts with host DDX18; this interaction redistributes host DDX18 to the cytoplasm. Interacts with host IFITM1. Interacts with host DDX5. Interacts with host DDX18; this interaction redistributes host DDX18 to the cytoplasm. Interacts with host OTULIN. Interacts with host LGALS3. The hydrophobic domains (HD) could mediate the membrane association of the replication complex and thereby alter the architecture of the host cell membrane. The OTU-like region is responsible for the deubiquitinating and deISGylation activities of Nsp2. Specific enzymatic cleavages in vivo by its own proteases yield mature proteins. Nsp1 is autocleaved into two subunits, Nsp1-alpha and Nsp1-beta. There are two alternative pathways for processing. Either nsp4-5 is cleaved, which represents the major pathway or the nsp5-6 and nsp6-7 are processed, which represents the minor pathway. The major pathway occurs when nsp2 acts as cofactor for nsp4. Produced by -1 ribosomal frameshifting at the 1a-1b genes boundary. Produced by conventional translation. Belongs to the arteriviridae polyprotein family.