Drug repurposing screen to identify inhibitors of the RNA polymerase (nsp12) and helicase (nsp13) from SARS-CoV-2 replication and transcription complex.

Coronaviruses contain one of the largest genomes among the RNA viruses, coding for 14-16 non-structural proteins (nsp) that are involved in proteolytic processing, genome replication and transcription, and four structural proteins that build the core of the mature virion. Due to conservation across coronaviruses, nsps form a group of promising drug targets as their inhibition directly affects viral replication and, therefore, progression of infection. A minimal but fully functional replication and transcription complex was shown to be formed by one RNA-dependent RNA polymerase (nsp12), one nsp7, two nsp8 accessory subunits, and two helicase (nsp13) enzymes.

Cryo-EM structure of rotavirus B NSP2 reveals its unique tertiary architecture.

Rotavirus (RV) NSP2 is a multifunctional RNA chaperone that exhibits numerous activities that are essential for replication and viral genome packaging. We performed an analysis that highlighted a distant relationship of NSP2 from rotavirus B (RVB) to proteins from other human RVs. We solved a cryo-electron microscopy structure of RVB NSP2 that shows structural differences with corresponding proteins from other human RVs.

Natural Compounds Inhibit SARS-CoV-2 nsp13 Unwinding and ATPase Enzyme Activities.

SARS-CoV-2 infection is still spreading worldwide, and new antiviral therapies are an urgent need to complement the approved vaccine preparations. SARS-CoV-2 nps13 helicase is a validated drug target participating in the viral replication complex and possessing two associated activities: RNA unwinding and 5'-triphosphatase. In the search of SARS-CoV-2 direct antiviral agents, we established biochemical assays for both SARS-CoV-2 nps13-associated enzyme activities and screened both and a small in-house library of natural compounds.

Liquid-liquid phase separation of the intrinsically disordered AB region of hRXRγ is driven by hydrophobic interactions.

Nuclear receptors (NRs) are a family of transcription factors that are regulated endogenously by small lipophilic ligands. Recently, liquid-liquid phase separation (LLPS) has appeared as a new aspect of NR function. In the human retinoid X receptor γ (hRXRγ), the inherently disordered AB region undergoes LLPS via homotypic multivalent interactions.

[Membraneless organelles and liquid-liquid phase separation – methods for their characterisation].

Membraneless organelles (MLOs) are a large group of intracellular compartments formed during various stages of a cell life. They are important subcellular structures which enable a cell performance of vital physiological processes including stress response. MLOs can be found in cytoplasm and organelles that are sealed by lipidic membrane, mainly in nucleus.

Nuclear immunophilin FKBP39 from Drosophila melanogaster drives spontaneous liquid-liquid phase separation.

The FKBP39 from Drosophila melanogaster is a multifunctional regulatory immunophilin. It contains two globular domains linked by a highly charged disordered region. The N-terminal domain shows homology to the nucleoplasmin core domain, and the C-terminal domain is characteristic for the family of the FKBP immunophilin ligand binding domain.

Intrinsically disordered N-terminal domain of the Helicoverpa armigera Ultraspiracle stabilizes the dimeric form via a scorpion-like structure.

Nuclear receptors (NRs) are a family of ligand-dependent transcription factors activated by lipophilic compounds. NRs share a common structure comprising three domains: a variable N-terminal domain (NTD), a highly conserved globular DNA-binding domain and a ligand-binding domain. There are numerous papers describing the molecular details of the latter two globular domains.