RESUMEN
SARS-CoV-2is the causative agent for the ongoing COVID19 pandemic, and this virus belongs to the Coronaviridae family. The nsp14 protein of SARS-CoV-2 houses a 3' to 5' exoribonuclease activity responsible for removing mismatches that arise during genome duplication. A homology model of nsp10-nsp14 complex was used to carry out in silico screening to identify molecules among natural products, or FDA approved drugs that can potentially inhibit the activity of nsp14. This exercise showed that ritonavir might bind to the exoribonuclease active site of the nsp14 protein. A model of the SARS-CoV-2-nsp10-nsp14 complex bound to substrate RNA showed that the ritonavir binding site overlaps with that of the 3' nucleotide of substrate RNA. A comparison of the calculated energies of binding for RNA and ritonavir suggested that the drug may bind to the active site of nsp14 with significant affinity. It is, therefore, possible that ritonavir may prevent association with substrate RNA and thus inhibit the exoribonuclease activity of nsp14. Overall, our computational studies suggest that ritonavir may serve as an effective inhibitor of the nsp14 protein. nsp14 is known to attenuate the inhibitory effect of drugs that function through premature termination of viral genome replication. Hence, ritonavir may potentiate the therapeutic properties of drugs such as remdesivir, favipiravir and ribavirin.
Asunto(s)
Antivirales/farmacología , Tratamiento Farmacológico de COVID-19 , Exorribonucleasas/antagonistas & inhibidores , Ritonavir/farmacología , SARS-CoV-2/efectos de los fármacos , Proteínas no Estructurales Virales/antagonistas & inhibidores , Secuencia de Aminoácidos , Antivirales/administración & dosificación , Antivirales/química , COVID-19/virología , Dominio Catalítico , Simulación por Computador , Evaluación Preclínica de Medicamentos , Sinergismo Farmacológico , Quimioterapia Combinada , Exorribonucleasas/química , Exorribonucleasas/genética , Genoma Viral/efectos de los fármacos , Humanos , Simulación de Dinámica Molecular , Pandemias , Ritonavir/administración & dosificación , Ritonavir/química , SARS-CoV-2/genética , SARS-CoV-2/fisiología , Proteínas no Estructurales Virales/química , Proteínas no Estructurales Virales/genética , Replicación Viral/efectos de los fármacosRESUMEN
DNA-driven hierarchical core-satellite nanostructures with plasmonic gold nanorod dimers and upconversion nanoparticles are fabricated. Once the core-satellite structure is activated, combined photothermal therapy and photodynamic therapy are carried out under the guidance of upconversion luminesce, T1 -weighted magnetic resonance, photoacoustics, and computed tomography imaging of tumors in vivo, which exhibit the multifunctional biological applications of the DNA-based self-assemblies.
Asunto(s)
Nanotubos/química , Neoplasias/terapia , Fototerapia , Acrilatos/química , Animales , Supervivencia Celular/efectos de los fármacos , Clorofilidas , Exorribonucleasas/química , Oro/química , Células HeLa , Humanos , Rayos Infrarrojos , Ratones , Ratones Desnudos , Nanopartículas/química , Nanotubos/toxicidad , Neoplasias/diagnóstico por imagen , Poliestirenos/química , Porfirinas/química , Porfirinas/uso terapéutico , Porfirinas/toxicidad , Fármacos Sensibilizantes a Radiaciones/química , Fármacos Sensibilizantes a Radiaciones/uso terapéutico , Fármacos Sensibilizantes a Radiaciones/toxicidad , Tomografía Computarizada por Rayos X , Trasplante HeterólogoRESUMEN
RNA transcripts in which all guanosine residues are replaced by inosine are degraded at a highly accelerated rate when incubated in extracts from HeLa cells, sheep uterus or pig brain. We report here the partial purification and characterization of a novel ribonuclease, referred to as I-RNase, that is responsible for the degradation of inosine-containing RNA (I-RNA). I-RNase is Mg2+ dependent and specifically degrades single-stranded I-RNA. Comparison of the Km of the enzyme for I-RNA with the Ki for inhibition by normal RNA suggests a approximately 300-fold preferential binding to I-RNA, which can account for the specificity of degradation. The site of cleavage by I-RNase is non-specific; I-RNase acts as a 3'-->5' exonuclease generating 5'-NMPs as products. The presence of alternative unconventional nucleotides in RNA does not result in degradation unless inosine residues are also present. We show that I-RNase is able to degrade RNAs that previously have been modified by the RED-1 double-stranded RNA adenosine deaminase (dsRAD). dsRADs destabilize dsRNA by converting adenosine to inosine, and some of these enzymes are interferon inducible. We therefore speculate that I-RNase in concert with dsRAD may form part of a novel cellular antiviral defence mechanism that acts to degrade dsRNA.