BRD4 inhibition exerts anti-viral activity through DNA damage-dependent innate immune responses

Abstract

Chromatin dynamics regulated by epigenetic modification is crucial in genome stability and gene expression. Various epigenetic mechanisms have been identified in the pathogenesis of human diseases. Here, we examined the effects of ten epigenetic agents on pseudorabies virus (PRV) infection by using GFP-reporter assays. Inhibitors of bromodomain protein 4 (BRD4), which receives much more attention in cancer than viral infection, was found to exhibit substantial anti-viral activity against PRV as well as a range of DNA and RNA viruses. We further demonstrated that BRD4 inhibition boosted a robust innate immune response. BRD4 inhibition also de-compacted chromatin structure and induced the DNA damage response, thereby triggering the activation of cGAS-mediated innate immunity and increasing host resistance to viral infection both in vitro and in vivo. Mechanistically, the inhibitory effect of BRD4 inhibition on viral infection was mainly attributed to the attenuation of viral attachment. Our findings reveal a unique mechanism through which BRD4 inhibition restrains viral infection and points to its potent therapeutic value for viral infectious diseases. Author summaryBRD4 has been well investigated in tumorigenesis for its contribution to chromatin remodeling and gene transcription. BRD4 inhibitors are used as promising chemotherapeutic drugs for cancer therapy. Here, we show a unique mechanism through which BRD4 inhibition broadly inhibits attachment of DNA and RNA viruses through DNA damage-dependent antiviral innate immune activation via the cGAS-STING pathway, in both cell culture and an animal model. STING-associated innate immune signaling has been considered to be a new possibility for cancer therapy, and STING agonists have been tested in early clinical trials. Our data identify BRD4 inhibitors as a potent therapy not only for viral infection but also for cancer immunotherapy. PLOS PATHOGENSPLOS Pathogens | https://doi.

Chicken bromodomain-containing protein 2 interacts with the Newcastle disease virus matrix protein and promotes viral replication

“…Unlike the functions of the BRD2/ET domain interacting with KSHV LANA and MLV integrase, NDV undergoes genomic replication, mRNA transcription, protein synthesis, and assembly of virus components in the cytoplasm, but the NDV M-chBRD2/ET interaction in the nucleus mainly assists in viral RNA synthesis and transcription until later in infection. Currently, accumulating studies have also revealed that the BRD2, BRD3 and BRD4 proteins participate in the host immune response against virus infection [ 51 – 53 ]. In our recent studies using quantitative proteomics analysis, we found that the parental virus rSS1GFP but not the mutant virus rSS1GFP-M/NLSm harbouring an NLS mutation in the M protein reduced the expression of the BRD2, BRD3 and BRD4 proteins to different degrees in virus-infected cells, suggesting that the decreased expression of BRD2, BRD3 and BRD4 was caused by early nuclear localization of the M protein [ 48 ].…”

Bromodomain Inhibitors as Therapeutics for Herpesvirus-Related Disease: All BETs Are Off?

“…Outside of human herpesviruses, a study on the swine alphaherpesvirus pseudorabies virus (PRV) has identified various means by which BRD4 inhibition can affect lytic virus infection. Use of three different compounds (JQ1, OTX015, and iBET-151), alongside confirmatory data with siRNA use, has recently shown that inhibition of BRD4, due to its importance in maintenance of higher-order chromatin structure (Wang et al, 2012 ), can lead to activation of the DNA damage response by chromatin de-compaction (Wang et al, 2020 ). In concert with induction of interferon-stimulated genes (ISGs), including IFN-β, DNA damage triggers activation of cGAS-mediated innate immunity and is able to attenuate attachment of the virus to the surface of BRDi-treated cells (Wang et al, 2020 ).…”

“…Use of three different compounds (JQ1, OTX015, and iBET-151), alongside confirmatory data with siRNA use, has recently shown that inhibition of BRD4, due to its importance in maintenance of higher-order chromatin structure (Wang et al, 2012 ), can lead to activation of the DNA damage response by chromatin de-compaction (Wang et al, 2020 ). In concert with induction of interferon-stimulated genes (ISGs), including IFN-β, DNA damage triggers activation of cGAS-mediated innate immunity and is able to attenuate attachment of the virus to the surface of BRDi-treated cells (Wang et al, 2020 ). In the absence of any effects to virus transcription, this BRDi-driven induction of an anti-viral state caused not only restriction of PRV infection in cell lines but also in an in vivo mouse model (Wang et al, 2020 ).…”

“…In concert with induction of interferon-stimulated genes (ISGs), including IFN-β, DNA damage triggers activation of cGAS-mediated innate immunity and is able to attenuate attachment of the virus to the surface of BRDi-treated cells (Wang et al, 2020 ). In the absence of any effects to virus transcription, this BRDi-driven induction of an anti-viral state caused not only restriction of PRV infection in cell lines but also in an in vivo mouse model (Wang et al, 2020 ). Importantly, this sole study provides further evidence that BET BRDi can have diverse effects on virus infections via various means but also that they might be used as a future therapy.…”

Host Epigenetics in Intracellular Pathogen Infections

“…The development of site-specific histone deacetylase (HADC) inhibitors, bromodomain inhibitors, histone lysine methyltransferase (HKMT) inhibitors represent new tools in the modulation of histone post-translational modifications. The HDAC inhibitors were found to be a promising approach to purge the reservoir of persistent HIV infection [ 119 ], whereas inhibitors of bromodomain protein 4 (BRD4) exhibited substantial anti-viral activity against pseudorabies virus as well as a wide range of DNA and RNA viruses [ 120 ]. Furthermore, improved understanding of clustered regularly interspaced short palindromic repeats (CRISPR) editing system enabling targeted modification of the epigenomemay result in expanded applications in the field of infectious diseases providing clarification of host and microbe interactions and help in the prevention and treatment of infectious diseases [ 121 ].…”