DNA Damage Response Differentially Affects BoHV-1 Gene Transcription in Cell Type-Dependent Manners

53BP1, a known chromatin-associated factor that promotes DNA damage repair, is differentially modulated during bovine herpesvirus 1 infection in vitro and in vivo

Bovine herpesvirus 1 (BoHV-1) productive infection induces the formation of DNA double-strand breaks (DSBs), the most severe form of DNA lesions in cultured cells. 53BP1, a chromatin-associated factor, plays an essential role in DNA damage repair. In this study, we demonstrated that BoHV-1 productive infection in bovine kidney (MDBK) cells increased the expression of phosphorylated form of H2AX protein (γH2AX) and promoted the formation of γH2AX foci in the nucleus, indicative of enhanced DNA lesions. However, despite the elevated total 53BP1 protein levels, its recruitment to the nucleus and formation of 53BP1 foci was impaired, suggesting the disruption of 53BP1-mediated DNA damage repair (DDR). Furthermore, immunohistochemistry (IHC) studies showed that γH2AX was readily detected in trigeminal ganglia (TG) neurons of New Zealand White rabbits during both acute infection (day 3) and dexamethasone (DEX)-stimulated reactivation from latency, indicating the occurrence of DNA damage in vivo. This was consistent with the substantial reduction of 53BP1 protein expression in these tissues. Interestingly, 53BP1 was detected in a subset of TG neurons from both mock-infected and latently infected rabbits, but the localization profile of 53BP1 looks largely different, suggesting that 53BP1 may play a role in viral latency. Taken together, our findings demonstrated that BoHV-1 lytic infection impaired 53BP1-dependent DNA damage repair through differing mechanisms in vitro and in vivo, potentially promoting the accumulation of DNA damage. Moreover, virus latency altered the 53BP1 localization, underscoring the importance of 53BP1 signaling in the virus pathogenicity.

Tegument protein UL3 of bovine herpesvirus 1 suppresses antiviral IFN-I signaling by targeting STING for autophagic degradation

Bovine herpesvirus 1 (BoHV-1) is a highly contagious pathogen which causes infectious bovine rhinotracheitis in cattle worldwide. Although it has the ability to evade the host's antiviral innate immune response and establish persistent latent infections, the mechanisms are not fully understood, especially the function of the tegument protein to escape innate immunity and participate in viral replication. In this study, we showed that overexpression of tegument protein UL3 facilitates BoHV-1 replication and suppresses the expression of type-I interferon (IFN-I) and IFN-stimulated genes. Then, STING was identified as the target by which UL3 inhibits the IFN-I signaling pathway, and STING was degraded through the UL3-induced autophagy pathway. Furthermore, overexpression of UL3 promotes the expression of the autophagy-related protein ATG101, thereby inducing autophagy. Further study showed that UL3 enhances the interaction between ATG101 and STING, and then the degradation of STING was reversed following ATG101 silencing in UL3-overexpressing cells during BoHV-1 infection. Our research results demonstrate a novel function of UL3 in regulating host's antiviral response and provide a potential mechanism for BoHV-1 immune evasion.

For better or worse: crosstalk of parvovirus and host DNA damage response

Parvoviruses are a group of non-enveloped DNA viruses that have a broad spectrum of natural infections, making them important in public health. NS1 is the largest and most complex non-structural protein in the parvovirus genome, which is indispensable in the life cycle of parvovirus and is closely related to viral replication, induction of host cell apoptosis, cycle arrest, DNA damage response (DDR), and other processes. Parvovirus activates and utilizes the DDR pathway to promote viral replication through NS1, thereby increasing pathogenicity to the host cells. Here, we review the latest progress of parvovirus in regulating host cell DDR during the parvovirus lifecycle and discuss the potential of cellular consequences of regulating the DDR pathway, targeting to provide the theoretical basis for further elucidation of the pathogenesis of parvovirus and development of new antiviral drugs.