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

Oxalicine B(1)is an a-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)/a-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 IC50values in the range of 4.0-19.9μmol/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.

SARS-CoV-2 hijacks cellular kinase CDK2 to promote viral RNA synthesis

The coronavirus disease 2019(COVID-19)pandemic has devastated global health.Identifying key host factors essential for SARS-CoV-2 RNA replication is expected to unravel cellular targets for the development of broad-spectrum antiviral drugs which have been quested for the preparedness of future viral outbreaks.Here,we have identified host proteins that associate with nonstructural protein 12(nsp12),the RNA-dependent RNA polymerase(RdRp)of SARS-CoV-2 using a mass spectrometry(MS)-based proteomic approach.Among the candidate factors,CDK2(Cyclin-dependent kinase 2),a member of cyclin-dependent kinases,interacts with nsp12 and causes its phosphorylation at T20,thus facilitating the assembly of the RdRp complex consisting of nsp12,nsp7 and nsp8 and promoting efficient synthesis of viral RNA.The crucial role of CDK2 in viral RdRp function is further supported by our observation that CDK2 inhibitors potently impair viral RNA synthesis and SARS-CoV-2 infection.Taken together,we have discovered CDK2 as a key host factor of SARS-CoV-2 RdRp complex,thus serving a promising target for the development of SARS-CoV-2 RdRp inhibitors.

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(EC50) value of 0.13 μmol/L.Computation modeling predicts that RAI-S-37 lands at the palm domain of RdRp and prevents conformational changes required for nucleotide incorporation by RdRp.In addition,combination of RAI-S-37 with remdesivir exhibits additive activity against antiSARS-CoV-2 RdRp.Together with the current data available on the safety and pharmacokinetics of corilagin as a medicinal herbal agent,these results demonstrate the potential of being developed into one of the much-needed SARS-CoV-2 therapeutics.

The CREB Regulated Transcription Coactivator 2 Suppresses HIV-1 Transcription by Preventing RNA PolⅡfrom Binding to HIV-1 LTR

The CREB-regulated transcriptional co-activators(CRTCs),including CRTC1,CRTC2 and CRTC3,enhance transcription of CREB-targeted genes.In addition to regulating host gene expression in response to cAMP,CRTCs also increase the infection of several viruses.While human immunodeficiency virus type 1(HIV-1)long terminal repeat(LTR)promoter harbors a cAMP response element and activation of the cAMP pathway promotes HIV-1 transcription,it remains unknown whether CRTCs have any effect on HIV-1 transcription and HIV-1 infection.Here,we reported that CRTC2 expression was induced by HIV-1 infection,but CRTC2 suppressed HIV-1 infection and diminished viral RNA expression.Mechanistic studies revealed that CRTC2 inhibited transcription from HIV-1 LTR and diminished RNA PolⅡoccupancy at the LTR independent of its association with CREB.Importantly,CRTC2 inhibits the activation of latent HIV-1.Together,these data suggest that in response to HIV-1 infection,cells increase the expression of CRTC2 which inhibits HIV-1 gene expression and may play a role in driving HIV-1 into latency.