Endogenous enzymatic activities of the avian reovirus S1133: identification of the viral capping enzyme.
Avian reovirus S1133 was shown to contain all the enzymatic activities required for the synthesis of mature viral transcripts, including a dsRNA-dependent RNA polymerase, a nucleoside triphosphate phosphohydrolase, an mRNA guanylyltransferase, and two mRNA methyltransferases. The virus used these enzymes both in vitro and in vivo to catalyze the synthesis of viral mRNAs containing a type-1 cap at their 5' ends. Incubation of reovirions with GTP led to the formation of an intermediate structure consisting of GMP bound to the viral core protein lambda 3 through a phosphoamide linkage. The reaction was specific for GTP and required the presence of both Mg2+ and inorganic pyrophosphatase. The GMP moiety can be transferred from the lambda 3-GMP complex to acceptors such as GDP and GTP, yielding GpppG and GppppG, respectively. Our results demonstrate that lambda 3 is the avian reovirus guanylyltransferase.
Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Santiago de Compostela, Spain.
J
J
Martinez-Costas
R
R
Varela
J
J
Benavente
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D001386:Azides / Q000378:metabolism; D002478:Cells, Cultured; D002642:Chick Embryo; D006152:Cyclic GMP / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D011756:Diphosphates / Q000378:metabolism; D005347:Fibroblasts; D007700:Kinetics; D009713:Nucleotidyltransferases / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis*; D012367:RNA, Viral / Q000096:biosynthesis; D012087:Reoviridae / Q000201:enzymology* / Q000378:metabolism; D012265:Ribonucleotides / Q000378:metabolism; D014158:Transcription, Genetic; D000098556:mRNA Guanylyltransferases
D001386:Azides; D011756:Diphosphates; D012333:RNA, Messenger; D012367:RNA, Viral; D012265:Ribonucleotides; C017040:8-azidoadenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D009713:Nucleotidyltransferases; D000098556:mRNA Guanylyltransferases; D012321:DNA-Directed RNA Polymerases; D006152:Cyclic GMP