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Since late 2016, a yellow fever virus (YFV) variant carrying a set of nine amino acid variations has circulated in South America. Three of them were mapped on the methyltransferase (MTase) domain of viral NS5 protein. To assess whether these changes affected viral infectivity, we synthesized YFV carrying the MTase of circulating lineage as well as its isoform with the residues of the previous strains (NS5 K101R, NS5 V138I, and NS5 G173S). We observed a slight difference in viral growth properties and plaque phenotype between the two synthetic YFVs. However, the MTase polymorphisms associated with the Brazilian strain of YFV (2016–2019) confer more susceptibility to the IFN-I. In addition, in vitro MTase assay revealed that the interaction between the YFV MTase and the methyl donor molecule (SAM) is altered in the Brazilian MTase variant. Altogether, the results reported here describe that the MTase carrying the molecular signature of the Brazilian YFV circulating since 2016 might display a slight decrease in its catalytic activity but virtually no effect on viral fitness in the parameters comprised in this study. The most marked influence of these residues stands in the immune escape against the antiviral response mediated by IFN-I. [ABSTRACT FROM AUTHOR]

Nordihydroguaiaretic acid (NDGA) is a major lignan metabolite found in Larrea spp., which are widely used in South America to treat various diseases. In breast tissue, estradiol is metabolized to the catechol estrogens such as 4-hydroxyestradiol (4-OHE2), which have been proposed to be cancer initiators potentially involved in mammary carcinogenesis. Catechol-O-methyltransferase (COMT) catalyzes the O-methylation of catechol estrogens to their less toxic methoxy derivatives, such as 4-O-methylestradiol (4-MeOE2). The present study investigated the novel biological activities of NDGA in relation to COMT and the effects of COMT inhibition by NDGA on 4-OHE2-induced cyto- and genotoxicity in MCF-7 human breast cancer cells. Two methoxylated metabolites of NDGA, 3-O-methylNDGA (3-MNDGA) and 4-O-methyl NDGA (4-MNDGA), were identified in the reaction mixture containing human recombinant COMT, NDGA, and cofactors. Km values for the COMT-catalyzed metabolism of NDGA were 2.6 µM and 2.2 µM for 3-MNDGA and 4-MNDGA, respectively. The COMT-catalyzed methylation of 4-OHE2 was inhibited by NDGA at an IC50 of 22.4 µM in a mixed-type mode of inhibition by double reciprocal plot analysis. Molecular docking studies predicted that NDGA would adopt a stable conformation at the COMT active site, mainly owing to the hydrogen bond network. NDGA is likely both a substrate for and an inhibitor of COMT. Comet and apurinic/apyrimidinic site quantitation assays, cell death, and apoptosis in MCF-7 cells showed that NDGA decreased COMT-mediated formation of 4-MeOE2 and increased 4-OHE2-induced DNA damage and cytotoxicity. Thus, NDGA has the potential to reduce COMT activity in mammary tissues and prevent the inactivation of mutagenic estradiol metabolites, thereby increasing catechol estrogen-induced genotoxicities. [ABSTRACT FROM AUTHOR]