RESUMEN
The genus of flavivirus includes many mosquito-borne human pathogens, such as Zika (ZIKV) and the four serotypes of dengue (DENV1-4) viruses, that affect billions of people as evidenced by epidemics and endemicity in many countries and regions in the world. Among the 10 viral proteins encoded by the viral genome, the nonstructural protein 1 (NS1) is the only secreted protein and has been used as a diagnostic biomarker. NS1 has also been an attractive target for its biotherapeutic potential as a vaccine antigen. This review focuses on the recent advances in the structural landscape of the secreted NS1 (sNS1) and its complex with monoclonal antibodies (mAbs). NS1 forms an obligatory dimer, and upon secretion, it has been reported to be hexametric (trimeric dimers) that could dissociate and bind to the epithelial cell membrane. However, high-resolution structural information has been missing about the high-order oligomeric states of sNS1. Several cryoEM studies have since shown that DENV and ZIKV recombinant sNS1 (rsNS1) are in dynamic equilibrium of dimer-tetramer-hexamer states, with tetramer being the predominant form. It was recently revealed that infection-derived sNS1 (isNS1) forms a complex of the NS1 dimer partially embedded in a High-Density Lipoprotein (HDL) particle. Structures of NS1 in complexes with mAbs have also been reported which shed light on their protective roles during infection. The biological significance of the diversity of NS1 oligomeric states remains to be further studied, to inform future research on flaviviral pathogenesis and the development of therapeutics and vaccines. Given the polymorphism of flavivirus NS1 across sample types with variations in antigenicity, we propose a nomenclature to accurately define NS1 based on the localization and origin.
Asunto(s)
Anticuerpos Monoclonales , Anticuerpos Antivirales , Flavivirus , Proteínas no Estructurales Virales , Proteínas no Estructurales Virales/inmunología , Proteínas no Estructurales Virales/química , Proteínas no Estructurales Virales/genética , Humanos , Anticuerpos Monoclonales/inmunología , Anticuerpos Monoclonales/química , Anticuerpos Antivirales/inmunología , Flavivirus/inmunología , Flavivirus/química , Flavivirus/genética , Animales , Virus Zika/inmunología , Virus Zika/genética , Virus Zika/química , Virus del Dengue/inmunología , Virus del Dengue/genética , Virus del Dengue/química , Multimerización de Proteína , Conformación ProteicaRESUMEN
Chemical modification of transcripts with 5' caps occurs in all organisms. Here, we report a systems-level mass spectrometry-based technique, CapQuant, for quantitative analysis of an organism's cap epitranscriptome. The method was piloted with 21 canonical caps-m7GpppN, m7GpppNm, GpppN, GpppNm, and m2,2,7GpppG-and 5 'metabolite' caps-NAD, FAD, UDP-Glc, UDP-GlcNAc, and dpCoA. Applying CapQuant to RNA from purified dengue virus, Escherichia coli, yeast, mouse tissues, and human cells, we discovered new cap structures in humans and mice (FAD, UDP-Glc, UDP-GlcNAc, and m7Gpppm6A), cell- and tissue-specific variations in cap methylation, and high proportions of caps lacking 2'-O-methylation (m7Gpppm6A in mammals, m7GpppA in dengue virus). While substantial Dimroth-induced loss of m1A and m1Am arose with specific RNA processing conditions, human lymphoblast cells showed no detectable m1A or m1Am in caps. CapQuant accurately captured the preference for purine nucleotides at eukaryotic transcription start sites and the correlation between metabolite levels and metabolite caps.
