Induction of the Human Protein P56 by Interferon, Double-Stranded RNA, or Virus Infection

Abstract

P56 is the most abundant protein induced by interferon (IFN) treatment of human cells. To facilitate studies on its induction pattern and cellular functions, we expressed recombinant P56 as a hexahistidine-tagged protein in Escherichia coli and purified it to apparent homogeneity using affinity chromatography. A polyclonal antibody raised against this recombinant protein was used to show that P56 is primarily a cytoplasmic protein. Cellular expression of P56 by transfection did not inhibit the replication of vesicular stomatitis virus and encephalomyocarditis virus. P56 synthesis was rapidly induced by IFN-beta, and the protein had a half-life of 6 h. IFN-gamma or poly(A)(+) could not induce the protein, but poly(I)-poly(C) or an 85-bp synthetic double-stranded RNA efficiently induced it. Similarly, infection of GRE cells, which are devoid of type I IFN genes, by vesicular stomatitis virus, encephalomyocarditis virus, or Sendai virus caused P56 induction. Surprisingly, Sendai virus could also induce P56 in the mutant cell line P2.1, which cannot respond to either IFN-alpha/beta or double-stranded RNA. Induction of P56 in the P2.1 cells and the parental U4C cells by virus infection was preceded by activation of IRF-3 as judged by its translocation to the nucleus from the cytoplasm.

Interferon type I gene expression in chronic hepatitis C

“…For some IFN-regulated genes, evidence has been found that their expression is induced by virus replication without a preceding type I IFN production. [33][34][35][36] These findings prompted us to investigate whether HCV replication in Huh-7 cells leads to the activation of IFN-regulated genes even if we could not detect an increase in the number of type I IFN mRNAs. As shown in Figure 4e, the presence of HCV replicons did not cause a general increase in the amount of MxA mRNAs although we observed that mRNA levels slightly varied between different cell clones.…”

Mouse p56 Blocks a Distinct Function of Eukaryotic Initiation Factor 3 in Translation Initiation

“…Viral stress conditions in cells are triggered by mechanisms commonly associated with a cell undergoing viral infection, such as the production of double-stranded RNA, the production of interferons, as well as other virus-mediated pathways that have yet to be elucidated. Previous studies from our laboratory have characterized the human viral stress-inducible protein p56, a 56-kDa protein (1). Human p56 (Hup56) has been shown to act as an inhibitor of protein synthesis through its association with the "e" subunit of eukaryotic initiation factor 3 (eIF3 1 ; the e subunit is also known as p48 or Int6) (2,3).…”

“…Previous studies from our laboratory have characterized the human viral stress-inducible protein p56, a 56-kDa protein (1). Human p56 (Hup56) has been shown to act as an inhibitor of protein synthesis through its association with the "e" subunit of eukaryotic initiation factor 3 (eIF3 1 ; the e subunit is also known as p48 or Int6) (2,3). We have shown recently (4) that the inhibitory activity of human p56 occurs at the step of ternary complex stabilization by eIF3, a key step in the initiation pathway for protein synthesis in eukaryotes.…”

Identification and expression analysis of two IFN-inducible genes in crucian carp (Carassius auratus L.)

“…Although all mammalian IFIT members have a simple promoter with two adjacent ISRE motifs (de Veer et al, 1998), several agents, including IFN, dsRNA, LPS, virus infection and retinoic acid (Lee et al, 1994;Yu et al, 1996;Niikura et al, 1997;Guo et al, 2000b), can induce their expression. IFI56 is the most strongly induced gene among all ISGs (Der et al, 1998) and displays diverse activated pathway by different stimuli (Guo et al, 2000b;Peters et al, 2002;Grandvaux et al, 2002).…”

“…IFI56 is the most strongly induced gene among all ISGs (Der et al, 1998) and displays diverse activated pathway by different stimuli (Guo et al, 2000b;Peters et al, 2002;Grandvaux et al, 2002). In response to dsRNA stimulation, human IFI56 is sufficient to be induced rapidly by activation of cellular latent IRF3 without ongoing protein synthesis (Bandyopadhyay et al, 1995;Peters et al, 2002).…”