Triad of human cellular proteins, IRF2, FAM111A, and RFC3, restrict replication of orthopoxvirus SPI-1 host-range mutants.
Viruses and their hosts can reach balanced states of evolution ensuring mutual survival, which makes it difficult to appreciate the underlying dynamics. To uncover hidden interactions, virus mutants that have lost defense genes may be used. Deletion of the gene that encodes serine protease inhibitor 1 (SPI-1) of rabbitpox virus and vaccinia virus, two closely related orthopoxviruses, prevents their efficient replication in human cells, whereas certain other mammalian cells remain fully permissive. Our high-throughput genome-wide siRNA screen identified host factors that prevent reproduction and spread of the mutant viruses in human cells. More than 20,000 genes were interrogated with individual siRNAs and those that prominently increased replication of the SPI-1 deletion mutant were subjected to a secondary screen. The top hits based on the combined data-replication factor C3 (RFC3), FAM111A, and interferon regulatory factor 2 (IRF2)-were confirmed by custom assays. The siRNAs to RFC1, RFC2, RFC4, and RFC5 mRNAs also enhanced spread of the mutant virus, strengthening the biological significance of the RFC complex as a host restriction factor for poxviruses. Whereas association with proliferating cell nuclear antigen and participation in processive genome replication are common features of FAM111A and RFC, IRF2 is a transcriptional regulator. Microarray analysis, quantitative RT-PCR, and immunoblotting revealed that IRF2 regulated the basal level expression of FAM111A, suggesting that the enhancing effect of depleting IRF2 on replication of the SPI-1 mutant was indirect. Thus, the viral SPI-1 protein and the host IRF2, FAM111A, and RFC complex likely form an interaction network that influences the ability of poxviruses to replicate in human cells.
Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.
Debasis
D
Panda
Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20850.
Daniel J
DJ
Fernandez
Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20850.
Madhu
M
Lal
Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20850.
Eugen
E
Buehler
Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892; bmoss@nih.gov.
Bernard
0000-0002-2154-8564
B
Moss
D000072283:A549 Cells; D006801:Humans; D050836:Interferon Regulatory Factor-2 / Q000378:metabolism*; D046228:Microarray Analysis; D009154:Mutation; D018155:Orthopoxvirus / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D011213:Poxviridae Infections / Q000378:metabolism / Q000821:virology; D011991:Receptors, Virus / Q000378:metabolism*; D051818:Replication Protein C / Q000378:metabolism*; D015843:Serpins / Q000235:genetics*; D014764:Viral Proteins / Q000235:genetics; D014779:Virus Replication
C579415:FAM111A protein, human; C494229:IRF2 protein, human; D050836:Interferon Regulatory Factor-2; C497562:RFC3 protein, human; D011991:Receptors, Virus; D015843:Serpins; D014764:Viral Proteins; D051818:Replication Protein C
DNA replication factors; RNAi screen; host range; interferon regulatory factor; poxviruses