Late-stage cascade of oxidation reactions during the biosynthesis of oxalicine B in Penicillium oxalicum

Oxalicine B ( 1) is an α-pyrone meroterpenoid with a unique bispirocyclic ring system derived from Penicillium oxalicum. The biosynthetic pathway of 15-deoxyoxalicine B ( 4) was preliminarily reported in Penicillium canescens, however, the genetic base and biochemical characterization of tailoring reactions for oxalicine B ( 1) has remained enigmatic. In this study, we characterized three oxygenases from the metabolic pathway of oxalicine B ( 1), including a cytochrome P450 hydroxylase OxaL, a hydroxylating Fe(II)/α-KG-dependent dioxygenase OxaK, and a multifunctional cytochrome P450 OxaB. Intriguingly, OxaK can catalyze various multicyclic intermediates or shunt products of oxalicines with impressive substrate promiscuity. OxaB was further proven via biochemical assays to have the ability to convert 15-hydroxdecaturin A ( 3) to 1 with a spiro-lactone core skeleton through oxidative rearrangement. We also solved the mystery of OxaL that controls C-15 hydroxylation. Chemical investigation of the wild-type strain and deletants enabled us to identify 10 metabolites including three new compounds, and the isolated compounds displayed potent anti-influenza A virus bioactivities exhibiting IC50 values in the range of 4.0-19.9 μmol/L. Our studies have allowed us to propose a late-stage biosynthetic pathway for oxalicine B ( 1) and create downstream derivatizations of oxalicines by employing enzymatic strategies.

Corilagin inhibits SARS-CoV-2 replication by targeting viral RNA-dependent RNA polymerase

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has become one major threat to human population health. The RNA-dependent RNA polymerase (RdRp) presents an ideal target of antivirals, whereas nucleoside analogs inhibitor is hindered by the proofreading activity of coronavirus. Herein, we report that corilagin (RAI-S-37) as a non-nucleoside inhibitor of SARS-CoV-2 RdRp, binds directly to RdRp, effectively inhibits the polymerase activity in both cell-free and cell-based assays, fully resists the proofreading activity and potently inhibits SARS-CoV-2 infection with a low 50% effective concentration (EC

Mechanism Underlying Increased Expression of a Member of the Serine/Threonine Kinase Family (Citron kinase) Induced by HIV-1 Infection / 病毒学报

Human immunodeficiency virus (HIV)-1 infection changes transcriptional profiles and regulates. the factors and machinery of the host that facilitate viral replication. Our previous study suggested that the serine/threonine kinase citron kinase (citK) promotes HIV-1 egress. To ascertain if HIV-1 infection affects citK expression in primary cells, peripheral blood mononuclear cells were infected with vesicular stomatitis virus G protein (VSV-G)-pseudotyped HIV-1 vector NL4-3-luc viruses, which resulted in remarkably increased expression of citK. citK overexpression led to a more than two-fold increase in HIV-1 production, whereas a significant decrease was observed when citK was depleted in CD4+ T cells. Infection with HIV-1 pseudoviruses induced increases in the mRNA and protein levels of citK by 2. 5- and 2. 7-fold in HEK293T cells, respectively. By cloning the 5-kb promoter of citK into a luciferase reporter system and transfecting the construct into HEK293T cells, enhanced luciferase activity was observed during HIV-1 infection. Taken together, these data demonstrate that HIV-1 infection upregulates citK expression at the transcriptional level, and thereby renders the host more susceptible to invasion by HIV-1.