Molecular and functional characterization of two infectious salmon anaemia virus (ISAV) proteins with type I interferon antagonizing activity.
In this study we characterize two proteins encoded by the two smallest genomic segments of the piscine orthomyxovirus infectious salmon anaemia virus (ISAV). Both proteins, encoded by the un-spliced ORF from genomic segment 7 (s7ORF1) and the larger ORF from segment 8 (s8ORF2), are involved in modulation of the type I interferon (IFN) response. The data suggests that the s7ORF1 protein is collinearly encoded, non-structural, contains no nuclear localisation signals, localises mainly to the cytoplasmic perinuclear area and does not bind single- or double-stranded RNA. On the other hand, genomic segment 8 uses a bicistronic coding strategy and the encoded s8ORF2 protein is a structural component of the viral particle. This protein contains two nuclear localisation signals, has a predominantly nuclear localisation, binds both double-stranded RNA and poly-A tailed single-stranded RNA, but not double-stranded DNA. In poly I:C stimulated salmon cells both ISAV proteins independently down-regulate the type I IFN promoter activity. Thus, ISAV counteracts the type I IFN response by the action of at least two of its gene products, rather than just one, as appears to be the case for other known members of the Orthomyxoviridae.
García-Rosado
Esther
E
Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, P.O. Box 8146 Dep., N-0033 Oslo, Norway. megarciar@uma.es
Markussen
Turhan
T
Kileng
Oyvind
O
Baekkevold
Espen S
ES
Robertsen
Børre
B
Mjaaland
Siri
S
Rimstad
Espen
E
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D007370:Interferon Type I / Q000037:antagonists & inhibitors*; D046829:Isavirus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics* / Q000502:physiology; D020317:Salmo salar / Q000821:virology*; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015678:Viral Structural Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D007370:Interferon Type I; D017361:Viral Nonstructural Proteins; D015678:Viral Structural Proteins