Interferon-Stimulated Poly(ADP-Ribose) Polymerases Are Potent Inhibitors of Cellular Translation and Virus Replication

Abstract

The innate immune response is the first line of defense against most viral infections. Its activation promotes cell signaling, which reduces virus replication in infected cells and leads to induction of the antiviral state in yet-uninfected cells. This inhibition of virus replication is a result of the activation of a very broad spectrum of specific cellular genes, with each of their products usually making a small but detectable contribution to the overall antiviral state. The lack of a strong, dominant function for each gene product and the ability of many viruses to interfere with the development of the antiviral response strongly complicate identification of the antiviral activity of the activated individual cellular genes. However, we have previously developed and applied a new experimental system which allows us to define a critical function of some members of the poly(ADP-ribose) polymerase (PARP) family in clearance of Venezuelan equine encephalitis virus mutants from infected cells. In this new study, we demonstrate that PARP7, PARP10, and the long isoform of PARP12 (PARP12L) function as important and very potent regulators of cellular translation and virus replication. The translation inhibition and antiviral effect of PARP12L appear to be mediated by more than one protein function and are a result of its direct binding to polysomes, complex formation with cellular RNAs (which is determined by both putative RNA-binding and PARP domains), and catalytic activity. IMPORTANCEThe results of this study demonstrate that interferon-stimulated gene products PARP7, PARP10, and PARP12L are potent inhibitors of the replication of Venezuelan equine encephalitis virus and other alphaviruses. The inhibitory functions are determined by more than a single mechanism, and one of them is based on the ability of these proteins to regulate cellular translation. Interference with the cellular translational machinery depends on the integrity of both the amino-terminal domain, containing a number of putative RNA-binding motifs, and the catalytic function of the carboxy-terminal PARP domain. The PARP-induced changes in translation efficiency appear to have a more potent effect on the synthesis of virus-specific proteins than on that of cellular proteins, thus making PARP-specific translational downregulation an important contributor to the overall development of the antiviral response.

PARP12, an Interferon-stimulated Gene Involved in the Control of Protein Translation and Inflammation

“…However, the link between this posttranslational modification and translational arrest is difficult to establish. In a previous study, a mutant form of PARP12, lacking a putative autoribosylation site has been generated based on sequence homology with an experimental validated site found on PARP10 (19). Although the catalytic activity of this mutant protein was not evaluated, the authors concluded from their studies that mutants lacking a catalytic activity and/or displaying a modified automodification site were equally inefficient in mediating translational arrest.…”

“…Accordingly, overexpression of PARP12 led to a general translation arrest in BHK-21 (19) and HEK293T cells (this study). The ZnF-containing domain played an important role in addressing PARP12 to SGs, as shown by altered localization of PARP12 mutant lacking the ZnF domain and of the fourth ZnF point mutated forms (see Fig.…”

“…The evidence accumulated to date favors a model in which PARP12 binds to a highly conserved mRNA structure, thus explaining its capacity to inhibit translation of virtually all cellular mRNAs (Ref. 19 and Fig. 5).…”

“…PARP12 belongs to a subgroup of PARP family members characterized by the presence of typical CCCH zinc fingers known to bind to viral (14,15), but also cytoplasmic RNAs (16,17). Accordingly, PARP12 has been recently found to accumulate in cytoplasmic stress granules known to regulate mRNA translation and stability in response to stress (18), and to inhibit viral translation by directly binding to polysomes of Venezuelan equine encephalitis infected cells (19). The present study was undertaken to better understand the potential biological role of the functional protein domains of PARP12.…”

Encephalitic Arboviruses: Emergence, Clinical Presentation, and Neuropathogenesis

“…RNaseL -/-mice exhibit higher WNV viral loads in peripheral tissues. Members of the poly (ADP-ribose) polymerase family block translation and replication of VEEV [130,131]. IFN-induced transmembrane protein family members play a key role in limiting bunyavirus, including RVFV and LACV, replication by inhibiting viral membrane fusion in the endosome [132].…”