The mengovirus leader protein suppresses alpha/beta interferon production by inhibition of the iron/ferritin-mediated activation of NF-kappa B.
In our studies on the biological function of the mengovirus leader protein, we identified a casein kinase II (CK-2) phosphorylation site in the protein. Here we report that the mengovirus leader protein can be phosphorylated by CK-2 in vitro. Expression of a recombinant leader protein in which the consensus CK-2 sequence around threonine 47 was disturbed resulted in a mutant protein that could no longer be phosphorylated. The CK-2 consensus sequence was modified by site-directed mutagenesis and subsequently introduced into a mengovirus cDNA clone to investigate the effect of the phosphorylation of the leader protein on virus replication and on the host cell response. Modifications by which the CK-2 consensus sequence was disturbed resulted in mutant viruses with reduced growth kinetics. We demonstrated that the integrity of the CK-2 phosphorylation site of the mengovirus leader protein was specifically related to the suppression of NF-kappa B activation and subsequent suppression of alpha/beta interferon production in infected cells. We also found that the integrity of the CK-2 phosphorylation site of the leader protein coincided with an increase of ferritin expression in the infected cell. These data indicate that the leader protein suppresses the iron-mediated activation of NF-kappa B and thereby inhibits alpha/beta interferon expression in the infected cell.
Zoll
Jan
J
Department of Medical Microbiology, Nijmegen Center for Molecular Life Sciences, University Medical Center Nijmegen, 6500 HB Nijmegen, The Netherlands. J.Zoll@ncmls.kun.nl
Melchers
Willem J G
WJ
Galama
Jochem M D
JM
van Kuppeveld
Frank J M
FJ
D000818:Animals; D001052:Apoferritins / Q000096:biosynthesis; D047390:Casein Kinase II; D005293:Ferritins / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D016898:Interferon-alpha / Q000096:biosynthesis*; D016899:Interferon-beta / Q000096:biosynthesis*; D007501:Iron / Q000502:physiology*; D008574:Mengovirus / Q000502:physiology*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021382:Protein Sorting Signals / Q000502:physiology*; D017382:Reactive Oxygen Species; D014764:Viral Proteins / Q000502:physiology*
D016898:Interferon-alpha; D016328:NF-kappa B; D021382:Protein Sorting Signals; D017382:Reactive Oxygen Species; D014764:Viral Proteins; D016899:Interferon-beta; D005293:Ferritins; D001052:Apoferritins; D007501:Iron; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases