Downregulation of Poly(ADP-Ribose) Polymerase 1 by a Viral Processivity Factor Facilitates Lytic Replication of Gammaherpesvirus

Abstract

In Kaposi's sarcoma-associated herpesvirus (KSHV), poly(ADP-ribose) polymerase 1 (PARP-1) acts as an inhibitor of lytic replication. Here, we demonstrate that KSHV downregulated PARP-1 upon reactivation. The viral processivity factor of KSHV (PF-8) interacted with PARP-1 and was sufficient to degrade PARP-1 in a proteasome-dependent manner; this effect was conserved in murine gammaherpesvirus 68. PF-8 knockdown in KSHV-infected cells resulted in reduced lytic replication upon reactivation with increased levels of PARP-1, compared to those in control cells. PF-8 overexpression reduced the levels of the poly(ADPribosyl)ated (PARylated) replication and transcription activator (RTA) and further enhanced RTA-mediated transactivation. These results suggest a novel viral mechanism for overcoming the inhibitory effect of a host factor, PARP-1, thereby promoting the lytic replication of gammaherpesvirus. IMPORTANCEGammaherpesviruses are important human pathogens, as they are associated with various kinds of tumors and establish latency mainly in host B lymphocytes. Replication and transcription activator (RTA) of Kaposi's sarcoma-associated herpesvirus (KSHV) is a central molecular switch for lytic replication, and its expression is tightly regulated by many host and viral factors. In this study, we investigated a viral strategy to overcome the inhibitory effect of poly(ADP-ribose) polymerase 1 (PARP-1) on RTA's activity. PARP-1, an abundant multifunctional nuclear protein, was downregulated during KSHV reactivation. The viral processivity factor of KSHV (PF-8) directly interacted with PARP-1 and was sufficient and necessary to degrade PARP-1 protein in a proteasome-dependent manner. PF-8 reduced the levels of PARylated RTA and further promoted RTA-mediated transactivation. As this was also conserved in another gammaherpesvirus, murine gammaherpesvirus 68, our results suggest a conserved viral modulation of a host inhibitory factor to facilitate its lytic replication. Gammaherpesviruses, such as Epstein-Barr virus (EBV), Kaposi's sarcoma-associated herpesvirus (KSHV), and murine gammaherpesvirus 68 (MHV-68), are associated with various malignancies and lymphoproliferative disorders (1, 2). Several cellular factors are known to regulate the lytic replication of gammaherpesvirus, ultimately contributing to viral pathogenesis (3, 4). Poly(ADP-ribose) polymerase 1 (PARP-1) is an abundant nuclear protein that catalyzes the poly(ADP-ribosyl)ation of target proteins acting in DNA repair, cell cycle control, apoptosis, and gene expression (5-7). In KSHV and MHV-68 infections, PARP-1 interacts with the poly(ADP-ribosyl)ate replication and transcription activator (RTA), the molecular switch of lytic replication, thereby repressing lytic viral replication (8-11). PARP-1 is also known to be a component of the viral replication complex, increasing viral genome replication (9, 12). Previously, we showed that open reading frame 49 (ORF49) of MHV-68 interacts with PARP-1, disrupting interactions between RTA and PARP-1 and furthe...

PARP1 restricts Epstein Barr Virus lytic reactivation by binding the BZLF1 promoter

“…In KSHV, PARP1 interacts with and PARylates Rta to repress Rta-mediated transactivation (Gwack et al, 2003). A recent study identified a KSHV protein that interacts with PARP1, targeting it for proteasomal degradation, and thus reducing levels of inhibitory PARylated-Rta (Cheong et al, 2015). Here, we identify a similar restrictive function for PARP1 in EBV.…”

“…Indeed, a body of evidence suggests that PARP1 may serve as a stress sensor—a function that would be especially relevant in regulating herpesvirus lytic reactivation (Mattiussi et al, 2007; Luo and Kraus, 2012). Reports in KSHV have shown that PARP1 is selectively downregulated by a lytic protein, and restricts KSHV lytic replication through various mechanisms, including poly(ADP-ribosyl)ation (PARylation) of the immediate early protein, Rta (Cheong et al, 2015; Gwack et al, 2003). …”

The impact of PARPs and ADP-ribosylation on inflammation and host–pathogen interactions

“…In addition, the processivity factor of KSHV and γHV-68, PF-8, binds to and targets PARP1 for degradation, which reduces PARylated RTA and enhances virus replication ( Fig. 4C; Noh et al 2012;Chung et al 2015). In contrast to the antiviral effects of PARPs during γ-herpesvirus infection, PARP activity seems to promote the replication of HSV-1, the prototype α-herpesvirus.…”

Multifaceted Role of PARP-1 in DNA Repair and Inflammation: Pathological and Therapeutic Implications in Cancer and Non-Cancer Diseases

“…Noteworthy, S. pyogens releases a NAD + glycohydrolase into the host cell that reduces PARP-1 activation and accumulation of PAR and interferes with inflammatory cytokine signaling and HMGB1 release [58]. PARP-1 and HMGB1 are also targeted by other pathogens such as gammaherpesviruses [59] and Chlamydia trachomatis [60] as a strategy to limit inflammation and evade immune response.…”