BRD4 is associated with raccoon polyomavirus genome and mediates viral gene transcription and maintenance of a stem cell state in neuroglial tumour cells

BRD4: an effective target for organ fibrosis

Fibrosis is an excessive wound-healing response induced by repeated or chronic external stimuli to tissues, significantly impacting quality of life and primarily contributing to organ failure. Organ fibrosis is reported to cause 45% of all-cause mortality worldwide. Despite extensive efforts to develop new antifibrotic drugs, drug discovery has not kept pace with the clinical demand. Currently, only pirfenidone and nintedanib are approved by the FDA to treat pulmonary fibrotic illness, whereas there are currently no available antifibrotic drugs for hepatic, cardiac or renal fibrosis. The development of fibrosis is closely related to epigenetic alterations. The field of epigenetics primarily studies biological processes, including chromatin modifications, epigenetic readers, DNA transcription and RNA translation. The bromodomain and extra-terminal structural domain (BET) family, a class of epigenetic readers, specifically recognizes acetylated histone lysine residues and promotes the formation of transcriptional complexes. Bromodomain-containing protein 4 (BRD4) is one of the most well-researched proteins in the BET family. BRD4 is implicated in the expression of genes related to inflammation and pro-fibrosis during fibrosis. Inhibition of BRD4 has shown promising anti-fibrotic effects in preclinical studies; however, no BRD4 inhibitor has been approved for clinical use. This review introduces the structure and function of BET proteins, the research progress on BRD4 in organ fibrosis, and the inhibitors of BRD4 utilized in fibrosis. We emphasize the feasibility of targeting BRD4 as an anti-fibrotic strategy and discuss the therapeutic potential and challenges associated with BRD4 inhibitors in treating fibrotic diseases.

Viral Hijacking of BET Proteins

Proteins of the bromodomain and exterminal domain (BET) family mediate critical host functions such as cell proliferation, transcriptional regulation, and the innate immune response, which makes them preferred targets for viruses. These multidomain proteins are best known as transcriptional effectors able to read acetylated histone and non-histone proteins through their tandem bromodomains. They also contain other short motif-binding domains such as the extraterminal domain, which recognizes transcriptional regulatory proteins. Here, we describe how different viruses have evolved to hijack or disrupt host BET protein function through direct interactions with BET family members to support their own propagation. The network of virus-BET interactions emerges as highly intricate, which may complicate the use of small-molecule BET inhibitors-currently in clinical development for the treatment of cancer and cardiovascular diseases-to treat viral infections.

Bovine Polyomavirus-1 (Epsilonpolyomavirus bovis): An Emerging Fetal Pathogen of Cattle That Causes Renal Lesions Resembling Polyomavirus-Associated Nephropathy of Humans

Bovine polyomavirus-1 (BoPyV-1, Epsilonpolyomavirus bovis) is widespread in cattle and has been detected in commercialized beef at supermarkets in the USA and Germany. BoPyV-1 has been questioned as a probable zoonotic agent with documented increase in seropositivity in people exposed to cattle. However, to date, BoPyV-1 has not been causally associated with pathology or disease in any animal species, including humans. Here we describe and illustrate pathological findings in an aborted bovine fetus naturally infected with BoPyV-1, providing evidence of its pathogenicity and probable abortigenic potential. Our results indicate that: (i) BoPyV-1 can cause severe kidney lesions in cattle, including tubulointerstitial nephritis with cytopathic changes and necrosis in tubular epithelial cells, tubular and interstitial inflammation, and interstitial fibroplasia; (ii) lesions are at least partly attributable to active viral replication in renal tubular epithelial cells, which have abundant intranuclear viral inclusions; (iii) BoPyV-1 large T (LT) antigen, resulting from early viral gene expression, can be detected in infected renal tubular epithelial cells using a monoclonal antibody raised against Simian Virus-40 polyomavirus LT antigen; and (iv) there is productive BoPyV-1 replication and virion assembly in the nuclei of renal tubular epithelial cells, as demonstrated by the ultrastructural observation of abundant arrays of viral particles with typical polyomavirus morphology. Altogether, these lesions resemble the “cytopathic-inflammatory pathology pattern” proposed in the pathogenesis of Human polyomavirus-1-associated nephropathy in immunocompromised people and kidney allograft recipients. Additionally, we sequenced the complete genome of the BoPyV-1 infecting the fetus, which represents the first whole genome of a BoPyV-1 from the Southern Hemisphere. Lastly, the BoPyV-1 strain infecting this fetus was isolated, causing a cytopathic effect in Madin–Darby bovine kidney cells. We conclude that BoPyV-1 is pathogenic to the bovine fetus under natural circumstances. Further insights into the epidemiology, biology, clinical relevance, and zoonotic potential of BoPyV-1 are needed.

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

Although the ubiquitous human herpesviruses (HHVs) are rarely associated with serious disease of the healthy host, primary infection and reactivation in immunocompromised individuals can lead to significant morbidity and, in some cases, mortality. Effective drugs are available for clinical treatment, however resistance is on the rise such that new anti-viral targets, as well as novel clinical treatment strategies, are required. A promising area of development and pre-clinical research is that of inhibitors of epigenetic modifying proteins that control both cellular functions and the viral life cycle. Here, we briefly outline the interaction of the host bromo- and extra-terminal domain (BET) proteins during different stages of the HHVs' life cycles while giving a full overview of the published work using BET bromodomain inhibitors (BRDis) during HHV infections. Furthermore, we provide evidence that small molecule inhibitors targeting the host BET proteins, and BRD4 in particular, have the potential for therapeutic intervention of HHV-associated disease.

ARV-825-induced BRD4 protein degradation as a therapy for thyroid carcinoma

Bromodomain-containing protein 4 (BRD4) is overexpressed in thyroid carcinoma, represents as an important therapeutic target. ARV-825 is a novel cereblon-based PROTAC (Proteolysis Targeting Chsimera) compound. It can induce fast and sustained BRD4 protein degradation. Its potential effect in human thyroid carcinoma cells was studied here. In TPC-1 cells and primary human thyroid carcinoma cells, ARV-825 potently inhibited cell viability, proliferation and migration. Furthermore, ARV-825 induced robust apoptosis activation in the thyroid carcinoma cells. ARV-825 induced BRD4 protein degradation and downregulation of its targets, including c-Myc, Bcl-xL and cyclin D1 in thyroid carcinoma cells. It was significantly more potent in inhibiting thyroid carcinoma cells than the known small molecule BRD4 inhibitors. In vivo studies demonstrated that ARV-825 oral administration potently suppressed TPC-1 xenograft tumor growth in severe combined immunodeficient mice. BRD4 protein degradation as well as c-Myc, Bcl-xL and cyclin D1 downregulation were detected in ARV-825-treated TPC-1 tumor tissues. Taken together, ARV-825 induces BRD4 protein degradation and inhibits thyroid carcinoma cell growth in vitro and in vivo.

Cancer in wildlife: patterns of emergence

Cancer is ubiquitous in wildlife, affecting animals from bivalves to pachyderms and cetaceans. Reports of increasing frequency demonstrate that neoplasia is associated with substantial mortality in wildlife species. Anthropogenic activities and global weather changes are shaping new geographical limitations for many species, and alterations in living niches are associated with visible examples of genetic bottlenecks, toxin exposures, oncogenic pathogens, stress and immunosuppression, which can all contribute to cancers in wild species. Nations that devote resources to monitoring the health of wildlife often do so for human-centric reasons, including for the prediction of the potential for zoonotic disease, shared contaminants, chemicals and medications, and for observing the effect of exposure from crowding and loss of habitat. Given the increasing human footprint on land and in the sea, wildlife conservation should also become a more important motivating factor. Greater attention to the patterns of the emergence of wildlife cancer is imperative because growing numbers of species are existing at the interface between humans and the environment, making wildlife sentinels for both animal and human health. Therefore, monitoring wildlife cancers could offer interesting and novel insights into potentially unique non-age-related mechanisms of carcinogenesis across species.

Procyonidae, Viverridae, Hyenidae, Herpestidae, Eupleridae, and Prionodontidae

This chapter covers the diseases and pathology of multiple taxonomic groups within the order Carnivora including Procyonidae several of the Feliformia carnivores. The overwhelming majority of knowledge about disease pathogenesis for these species is biased toward raccoons and concern for disease spread to humans and companion animals. Procyonids and feliform carnivores are ubiquitous in their environments and share habitat and environmental resources with other nondomestic and domestic carnivores and humans. As reservoirs for a number of important multispecies or zoonotic pathogens, surveys for pathogens that may be harbored or vectored by several of the species in this chapter, for example, raccoons (e.g., canine distemper virus, rabies, and leptospirosis) and civets (e.g., SARS coronavirus), have been active areas of investigation. Unfortunately, less research has focused on the potential effects of these pathogens on their hosts.

Chemical probes targeting epigenetic proteins: Applications beyond oncology

Epigenetic chemical probes are potent, cell-active, small molecule inhibitors or antagonists of specific domains in a protein; they have been indispensable for studying bromodomains and protein methyltransferases. The Structural Genomics Consortium (SGC), comprising scientists from academic and pharmaceutical laboratories, has generated most of the current epigenetic chemical probes. Moreover, the SGC has shared about 4 thousand aliquots of these probes, which have been used primarily for phenotypic profiling or to validate targets in cell lines or primary patient samples cultured in vitro. Epigenetic chemical probes have been critical tools in oncology research and have uncovered mechanistic insights into well-established targets, as well as identify new therapeutic starting points. Indeed, the literature primarily links epigenetic proteins to oncology, but applications in inflammation, viral, metabolic and neurodegenerative diseases are now being reported. We summarize the literature of these emerging applications and provide examples where existing probes might be used.