The African Swine Fever Virus DP71L Protein Recruits the Protein Phosphatase 1 Catalytic Subunit To Dephosphorylate eIF2α and Inhibits CHOP Induction but Is Dispensable for These Activities during Virus Infection

Abstract

The African swine fever virus (ASFV) DP71L protein is present in all isolates as either a short form of 70 to 72 amino acids or a long form of about 184 amino acids, and both of these share sequence similarity to the C-terminal domain of the herpes simplex virus ICP34.5 protein and cellular protein GADD34. In the present study we expressed DP71L in different mammalian cells and demonstrated that DP71L causes dephosphorylation of eukaryotic translation initiation factor 2 alpha (eIF2␣) in resting cells and during chemical-induced endoplasmic reticulum stress and acts to enhance expression of cotransfected reporter genes. We showed that DP71L binds to all the three isoforms (␣, ␤, and ␥) of the protein phosphatase 1 catalytic subunit (PP1c) and acts by recruiting PP1c to eIF2␣. We also showed that DP71L inhibits the induction of ATF4 and its downstream target, CHOP. We investigated the eIF2␣ phosphorylation status and induction of CHOP in porcine macrophages infected by two ASFV field isolates, Malawi Lil20/1 and Benin 97/1, and two DP71L deletion mutants, Malawi⌬NL and E70⌬NL. Our results showed that deletion of the DP71L gene did not cause an increase in the level of eIF2␣ phosphorylation or induction of CHOP, indicating that DP71L is not the only factor required by the virus to control the phosphorylation level of eIF2␣ during infection. We therefore hypothesize that ASFV has other mechanisms to prevent the eIF2␣ phosphorylation and the subsequent protein synthesis inhibition.

Regulation of de novo translation of host cells by manipulation of PERK/PKR and GADD34-PP1 activity during Newcastle disease virus infection

“…Moreover, some viruses encode viral proteins mimicking the function of GADD34. These viral GADD34 mimicking proteins include transmissible gastroenteritis virus nonstructural protein 7 (Cruz et al, 2011), Herpes simplex virus 1 ICP34.5 (He et al, 1998), African swine fever virus DPL71 protein (Zhang et al, 2010a) and porcine alpha-herpes-virus pseudorabies virus early viral protein IE180 (Van Opdenbosch et al, 2012). GADD34 helps PP1 to dephosphorylate eIF2a and maintain protein synthesis; meanwhile, it also aids PP1 dephosphorylate RIG-I/MDA5, TAK1, TBK1 and IKKb (Gu et al, 2014;Li et al, 2008;Qu et al, 2015;Wies et al, 2013).…”

Pacmanvirus, a New Giant Icosahedral Virus at the Crossroads between Asfarviridae and Faustoviruses

“…In the case of nucleotide metabolism, transcription, replication, repair, and some other structural proteins, we detected that the structural gene complex associated in ASFV with the capsid maturation process, as well as RNA polymerase subunits, has conserved homologs in kaumoebavirus, faustoviruses, and pacmanvirus. However, ASFV genomes possess at least 8 particular genes, i.e., the IAP apoptosis inhibitor A224L gene (21), the Bcl-2 apoptosis inhibitor A179L gene (22), the inhibitor of host gene transcription A238L gene (23), the C-type lectin-like EP153R gene (24), the CD2-like hemadsorption to infected cells EP402R gene (25), the similar neurovirulence factor DP71L gene (26), the NifS-like QP383R gene, and the phosphoprotein binding ribonucleoprotein-K CP204L gene. All of these are involved in host cell interactions, but only one gene, QP383R, seems to have orthologs in faustoviruses and pacmanvirus.…”

Herpes Simplex Virus 2 Infection Impacts Stress Granule Accumulation

“…There are many examples of viral gene products that act as antagonists of PKR (37), as well as at least one example of a viral gene product that acts as an antagonist of the related stress-activated kinase, the PKR-like endoplasmic reticulum kinase, PERK (53). Viruses can also directly modulate the phosphorylation status of eIF2␣ (27,66).…”