PLK3 facilitates replication of swine influenza virus by phosphorylating viral NP protein

Species-specific RNA barcoding technology for rapid and accurate identification of four types of influenza virus

BACKGROUND

The influenza virus (IV) is responsible for seasonal flu epidemics. Constant mutation of the virus results in new strains and widespread reinfections across the globe, bringing great challenges to disease prevention and control. Research has demonstrated that barcoding technology efficiently and cost-effectively differentiates closely related species on a large scale. We screened and validated species-specific RNA barcode segments based on the genetic relationships of four types of IVs, facilitating their precise identification in high-throughput sequencing viral samples.

RESULTS

Through the analysis of single nucleotide polymorphism, population genetic characteristics, and phylogenetic relationships in the training set, 7 IVA type, 29 IVB type, 40 IVC type, and 5 IVD type barcode segments were selected. In the testing set, the nucleotide-level recall rate for all barcode segments reached 96.86%, the average nucleotide-level specificity was approximately 55.27%, the precision rate was 100%, and the false omission rate was 0%, demonstrating high accuracy, specificity, and generalization capabilities for species identification. Ultimately, all four types of IVs were visualized in a combination of one-dimensional and two-dimensional codes and stored in an online database named Influenza Virus Barcode Database (FluBarDB, http://virusbarcodedatabase.top/database/index.html ).

CONCLUSION

This study validates the effective application of RNA barcoding technology in the detection of IVs and establishes criteria and procedures for selecting species-specific molecular markers. These advancements enhance the understanding of the genetic and epidemiological characteristics of IVs and enable rapid responses to viral genetic mutations.

Positive Regulation of Cellular Proteins by Influenza Virus for Productive Infection

Influenza viruses cause annual epidemics and occasional pandemics through respiratory tract infections, giving rise to substantial morbidity and mortality worldwide. Influenza viruses extensively interact with host cellular proteins and exploit a variety of cellular pathways to accomplish their infection cycle. Some of the cellular proteins that display negative effects on the virus are degraded by the virus. However, there are also various proteins upregulated by influenza at the expression and/or activation levels. It has been well-established that a large number of host antiviral proteins such as type I interferon-stimulated genes are elevated by viral infection. On the other hand, there are also many cellular proteins that are induced directly by the virus, which are considered as pro-viral factors and often indispensable for rigorous viral propagation or pathogenicity. Here, we review the recent advances in our understanding of the cellular factors deemed to be upregulated and utilized by the influenza virus. The focus is placed on the functions of these pro-viral proteins and the mechanisms associated with promoting viral amplification, evading host immunity, or enhancing viral pathogenicity. Investigating the process of how influenza viruses hijack cellular proteins could provide a framework for inventing the host-factor-targeted drugs to conquer influenza.

Phosphorylation of PA at serine 225 enhances viral fitness of the highly pathogenic H5N1 avian influenza virus in mice

Currently, there is increasing spillover of highly pathogenic H5N1 avian influenza virus (AIV) to mammals, raising a concern of pandemic threat about this virus. Although the function of PA protein of the influenza virus is well understood, the understanding of how phosphorylation regulates this protein and influenza viral life cycle is still limited. We previously identified PA S225 as the phosphorylation site in the highly pathogenic H5N1 AIV. In this study, we investigated the role of phosphorylation in regulating PA function and viral fitness through dephosphorylation (PA S225A) or continuous phosphorylation (PA S225E)-mimetic mutation of PA S225. Structure analysis revealed that PA S225A or PA S225E mutation had no obvious effect on the structure of PA protein. Replication assay in vitro showed that PA S225A phosphorylation-ablative mutation significantly inhibited virus replication both in mammalian and avian-derived cells, while PA S225E enhanced viral replication in these cells. Correspondingly, PA S225A dephosphorylation significantly attenuated viral replication and virulence in mice, while PA S225E enhanced these aspects in mice. Mechanistically, PA S225A mutation significantly decreased viral polymerase activity, disabled viral ribonucleoprotein complex (vRNP) assembly and attenuated PA nuclear accumulation. Altogether, our study directly suggested that phosphorylation of PA protein at site S225 enhances viral fitness of the highly pathogenic H5N1 virus in mammals by assuring effective vRNP activity, providing a framework for further study of phosphorylation events in influenza virus life cycle.

Progress with polo-like kinase (PLK) inhibitors: a patent review (2018-present)

INTRODUCTION

Polo-like kinases (PLKs) have five isoforms, all of which play crucial roles in cell cycle and cell proliferation, offering opportunities for drug design and treatment of cancers and other related diseases. Notably, PLK1 and PLK4 have been extensively investigated as cancer drug targets. One distinctive feature of PLKs is the presence of a unique polo-box domain (PBD), which regulates kinase activity and subcellular localization. This provides possibilities for specifically targeting PLKs.

AREA COVERED

This article provides an overview of the roles of PLKs in various cancers and related diseases, as well as the drug development involving PLKs, with a particular focus on PLK1 and PLK4. It summarizes the PLK1 and PLK4 inhibitors that have been disclosed in patents or literature (from 2018 - present), which were sourced from SciFinder and WIPO database.

EXPERT OPINION

After two decades of drug development on PLKs, several drugs progressed into clinical trials for the treatment of many cancers; however, none of them has been approved yet. Further elucidating the mechanisms of PLKs and identifying and developing highly selective ATP-competitive inhibitors, highly potent drug-like PBD inhibitors, degraders, etc. may provide new opportunities for cancer therapy and the treatment for several nononcologic diseases. PLKs inhibition-based combination therapies can be another helpful strategy.