Two basic motifs of reovirus sigma 3 protein are involved in double-stranded RNA binding.
It has been reported that the sigma 3 protein of reovirus can exert an inhibitory effect on the cellular double-stranded RNA (dsRNA) activated protein kinase. Activation of this kinase is thought to be a general mechanism mediating a cellular antiviral response. This enzyme can also be activated upon transfection, resulting in translational inhibition of plasmid-encoded mRNAs. sigma 3 has an affinity for dsRNA postulated to be responsible for antikinase activity. In the present study, site-directed mutagenesis was performed on two basic regions previously suggested as dsRNA-binding motifs and the mutant sigma 3 proteins were then expressed in COS cells. These experiments revealed that both motifs are involved in sigma 3 attachment to RNA. Expression of the mutants lacking RNA-binding capability is stimulated by coexpression of another dsRNA-binding protein, the E3L vaccinia virus protein. These results support a model in which the attachment to dsRNA is directly responsible for the trans-stimulating effect of sigma 3 on expression of cotransfected genes.
Mabrouk
T
T
Département de microbiologie et immunologie, Université de Montréal, Canada.
Danis
C
C
Lemay
G
G
D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D036022:Capsid Proteins; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D012330:RNA, Double-Stranded / Q000378:metabolism*; D016601:RNA-Binding Proteins; D012087:Reoviridae / Q000378:metabolism*; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism*
D036022:Capsid Proteins; D012330:RNA, Double-Stranded; D016601:RNA-Binding Proteins; D014764:Viral Proteins; C053179:sigma protein 3, Reovirus