Lytic Reactivation of the Kaposi’s Sarcoma-Associated Herpesvirus (KSHV) Is Accompanied by Major Nucleolar Alterations

Ribosomes: from conserved origin to functional/medical mobility and heterogeneity

Ribosomes, the molecular machines that translate the genetic code from mRNA into proteins in all living cells, are highly structurally conserved across all domains of life and hence are believed to have evolved from a structurally unified pocket. Initially perceived as uniform cellular factories for protein synthesis, currently, ribosomes have emerged as more complex entities. Structural, medical and biochemical studies, including ours, have revealed significant variability in their compositions across tissues, species, functions and developmental stages, highlighting their multifunctional potential. Moreover, the diversity of ribosomes, their components and their associated biological factors challenge the traditional perception of uniform interactions under various conditions, including stress, and expose their mobility and heterogeneity. Evidence for their functional diversity can be seen even in modifications of ribosomal genes, where minor changes may play critical roles under stress or may lead to diseases called ribosomopathies, including Diamond-Blackfan anaemia, some types of cancer and Alzheimer's disease. Thus, through in-depth structural explorations, we improve the understanding of the mechanisms regulating protein biosynthesis in response to various environmental stressors. These findings should potentially reshape the perceptions of the various ribosomal roles.This article is part of the discussion meeting issue 'Ribosome diversity and its impact on protein synthesis, development and disease'.

Epigenetic and epitranscriptomic regulation during oncogenic γ-herpesvirus infection

Oncogenic gamma herpesviruses, including Epstein-Barr Virus (EBV) and Kaposi's Sarcoma-associated Herpesvirus (KSHV), are opportunistic cancer-causing viruses and induces oncogenesis through complex mechanisms, which involves manipulation of cellular physiology as well as epigenetic and epitranscriptomic reprogramming. In this review, we describe the intricate processes by which these viruses interact with the epigenetic machinery, leading to alterations in DNA methylation, histone modifications, and the involvement of non-coding RNAs. The key viral proteins such as EBNA1 and LMP1 encoded by EBV; LANA and vGPCR encoded by KSHV; play pivotal roles in these modifications by interacting with host factors, and dysregulating signaling pathways. The resultant reprogramming can lead to activation of oncogenes, silencing of tumor suppressor genes, and evasion of the immune response, which ultimately contributes to the oncogenic potential of these viruses. Furthermore, in this review, we explore current therapeutic strategies targeting these epigenetic alterations and discuss future directions for research and treatment. Through this comprehensive examination of the epigenetic and epitranscriptomic reprogramming mechanisms employed by oncogenic gamma herpesviruses, we aim to provide valuable insights into potential avenues for novel therapeutic interventions.

Nucleolin Regulates the Expression of Kaposi's Sarcoma-Associated Herpesvirus' Latency-Associated Nuclear Antigen through G-Quadruplexes in the mRNA

Kaposi's sarcoma-associated herpesvirus (KSHV) establishes life-long latent infection and is linked to several human malignancies. Latency-associated nuclear antigen (LANA) is highly expressed during latency, and is responsible for the replication and maintenance of the viral genome. The expression of LANA is regulated at transcriptional/translational levels through multiple mechanisms, including the secondary structures in the mRNA sequence. LANA mRNA has multiple G-quadruplexes (G4s) that are bound by multiple proteins to stabilize/destabilize these secondary structures for regulating LANA. In this manuscript, we demonstrate the role of Nucleolin (NCL) in regulating LANA expression through its interaction with G-quadruplexes of LANA mRNA. This interaction reduced LANA's protein expression through the sequestration of mRNA into the nucleus, demonstrated by the colocalization of G4-carrying mRNA with NCL. Furthermore, the downregulation of NCL, by way of a short hairpin, showed an increase in LANA translation following an alteration in the levels of LANA mRNA in the cytoplasm. Overall, the data presented in this manuscript showed that G-quadruplexes-mediated translational control could be regulated by NCL, which can be exploited for controlling KSHV latency.

Mechanism of herpesvirus UL24 protein regulating viral immune escape and virulence

Herpesviruses have evolved a series of abilities involved in the process of host infection that are conducive to virus survival and adaptation to the host, such as immune escape, latent infection, and induction of programmed cell death for sustainable infection. The herpesvirus gene UL24 encodes a highly conserved core protein that plays an important role in effective viral infection. The UL24 protein can inhibit the innate immune response of the host by acting on multiple immune signaling pathways during virus infection, and it also plays a key role in the proliferation and pathogenicity of the virus in the later stage of infection. This article reviews the mechanism by which the UL24 protein mediates herpesvirus immune escape and its effects on viral proliferation and virulence by influencing syncytial formation, DNA damage and the cell cycle. Reviewing these studies will enhance our understanding of the pathogenesis of herpesvirus infection and provide evidence for new strategies to combat against viral infection.