The replicase polyprotein of coronaviruses 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. The papain-like proteinase 1 (PLP1) and papain-like proteinase 2 (PLP2) are responsible for the cleavages located at the N-terminus of the replicase polyprotein. In addition, PLP2 possesses a deubiquitinating/deISGylating activity and processes both 'Lys-48'- and 'Lys-63'-linked polyubiquitin chains from cellular substrates. PLP2 also antagonizes innate immune induction of type I interferon by blocking the nuclear translocation of host IRF-3 (By similarity). Responsible for the majority of cleavages as it cleaves the C-terminus of replicase polyprotein at 11 sites. Recognizes substrates containing the core sequence [ILMVF]-Q-|-[SGACN]. Inhibited by the substrate-analog Cbz-Val-Asn-Ser-Thr-Leu-Gln-CMK. Also contains an ADP-ribose-1''-phosphate (ADRP)-binding function (By similarity). The helicase which contains a zinc finger structure displays RNA and DNA duplex-unwinding activities with 5' to 3' polarity. ATPase activity is strongly stimulated by poly(U), poly(dT), poly(C), poly(dA), but not by poly(G) (By similarity). The exoribonuclease acts on both ssRNA and dsRNA in a 3' to 5' direction. Nsp7-nsp8 hexadecamer may possibly confer processivity to the polymerase, maybe by binding to dsRNA or by producing primers utilized by the latter. Nsp9 is a ssRNA-binding protein. 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). 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). a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) ATP + H2O = ADP + H(+) + phosphate ATP + H2O = ADP + H(+) + phosphate a 5'-end (N(7)-methyl 5'-triphosphoguanosine)-ribonucleoside in mRNA + S-adenosyl-L-methionine = a 5'-end (N(7)-methyl 5'-triphosphoguanosine)-(2'-O-methyl-ribonucleoside) in mRNA + H(+) + S-adenosyl-L-homocysteine uridylyl-uridylyl-ribonucleotide-RNA = a 3'-end uridylyl-2',3'-cyclophospho-uridine-RNA + a 5'-end dephospho-ribonucleoside-RNA Likely affects Nsp15 binding to RNA. 3CL-PRO exists as monomer and homodimer. Eight copies of nsp7 and eight copies of nsp8 assemble to form a heterohexadecamer. Nsp9 is a dimer. Nsp10 forms a dodecamer (By similarity). nsp7, nsp8, nsp9 and nsp10 are localized in cytoplasmic foci, largely perinuclear. Late in infection, they merge into confluent complexes (By similarity). nsp7, nsp8, nsp9 and nsp10 are localized in cytoplasmic foci, largely perinuclear. Late in infection, they merge into confluent complexes (By similarity). nsp7, nsp8, nsp9 and nsp10 are localized in cytoplasmic foci, largely perinuclear. Late in infection, they merge into confluent complexes (By similarity). nsp7, nsp8, nsp9 and nsp10 are localized in cytoplasmic foci, largely perinuclear. Late in infection, they merge into confluent complexes (By similarity). The helicase interacts with the N protein in membranous complexes and colocalizes with sites of synthesis of new viral RNA. The hydrophobic domains (HD) could mediate the membrane association of the replication complex and thereby alter the architecture of the host cell membrane. Specific enzymatic cleavages in vivo by its own proteases yield mature proteins. 3CL-PRO and PL-PRO proteinases are autocatalytically processed (By similarity). Produced by -1 ribosomal frameshifting at the 1a-1b genes boundary. Produced by conventional translation. Belongs to the coronaviruses polyprotein 1ab family.