Biology subjects

Tripathi, S. K.

Publications and source records attributed to Tripathi, S. K..

3 recordsLinked to original sources

bioRxiv2021

6',6'-Difluoro-aristeromycin is a potent inhibitor of MERS-coronavirus replication

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has highlighted the lack of treatments to combat infections with human or (potentially) zoonotic CoVs. Thus, it is critical to develop and evaluate antiviral compounds that either directly target CoV functions or modulate host functions involved in viral replication. Here, we demonstrate that low-micromolar concentrations of 6',6'-difluoro-aristeromycin (DFA), an adenosine nucleoside analogue, strongly inhibit the replication of Middle East respiratory syndrome coronavirus (MERS-CoV) in a cell-based infection assay. DFA was designed to target S-adenosylhomocysteine (SAH) hydrolase and, consequently, may affect intracellular levels of the methyl donor S-adenosylmethionine, which is used by two CoV methyltransferases involved in the capping of the 5 end of the viral mRNAs. Passaging of wild-type MERS-CoV in the presence of DFA selected a virus population with a [~]100-fold decreased DFA sensitivity, which carried various amino acid substitutions in viral nonstructural proteins (nsps). Specifically, mutations were present in the RNA polymerase subunit (nsp12) and in nsp13, the helicase subunit containing a nucleoside triphosphate hydrolase activity that has been implicated in CoV capping. We hypothesize that DFA directly or indirectly affects viral cap methylation, either by inhibiting the viral enzymes involved or by binding to SAH hydrolase. We also evaluated the antiviral activity of DFA against other betacoronaviruses, but found it to have limited impact on their replication, while being quite cytotoxic to the Calu-3 cells used for this comparison. Nevertheless, our results justify the further characterization of DFA derivatives as an inhibitor of MERS-CoV replication. ImportanceCurrently, there is a lack of antiviral drugs with proven efficacy against human CoV infections including the MERS-CoV that is endemic in the Middle East, the pandemic SARS-CoV-2 and potential future zoonotic CoV. This highlights the importance to investigate new drug targets and identify compounds that can be used to inhibit CoV replication. In this study, we characterize the inhibitory effect of DFA on MERS-CoV replication by phenotypic studies, time-of-addition studies, and the generation and genotyping of a DFA-resistant virus population. Our results revealed that DFA needs further improvement to reduce its cytotoxic side-effects and potentially enhance its broad-spectrum activity. Despite this observation, we think that DFA can be used to understand the function and metabolic interactions of the CoV RNA-synthesizing machinery, or as a starting point for the design of new compounds of the same class.

microbiology↗

bioRxiv2021

Mapping Interactome Networks of FOSL1 and FOSL2 in Human Th17 Cells

Dysregulated function of Th17 cells has implications in immunodeficiencies and autoimmune disorders. Th17 cell-differentiation is orchestrated by a complex network of transcription factors, including several members of the activator protein (AP-1) family. Among these, FOSL1 and FOSL2 influence the effector responses of Th17 cells. However, the molecular mechanisms underlying these functions are unclear, owing to the poorly characterized protein interaction networks of these factors. Here, we establish the first interactomes of FOSL1 and FOSL2 in human Th17 cells, using affinity purification-mass spectrometry analysis. In addition to the known JUN proteins, we identified several novel binding partners of FOSL1 and FOSL2. Gene ontology analysis found a major fraction of these interactors to be associated with RNA binding activity, which suggests new mechanistic links. Intriguingly, 29 proteins were found to share interactions with FOSL1 and FOSL2, and these included key regulators of Th17-fate. We further validated the binding partners identified in this study by using parallel reaction monitoring targeted mass-spectrometry and other methods. Our study provides key insights into the interaction-based signaling mechanisms of FOSL factors that potentially govern Th17 cell-differentiation and associated pathologies.

immunology↗

bioRxiv2021

The AP-1 factors FOSL1 and FOSL2 co-regulate human Th17 responses

Th17 cells protect mucosal barriers, but their aberrant activity can cause autoimmunity. Molecular networks dictating human Th17 function are largely unexplored, and this hinders disease-studies. Here, we investigated the roles of the AP-1 factors, FOSL1 and FOSL2, in inducing human Th17 responses. Transient knockdown and over-expression strategies found the two proteins to inhibit Th17-cell identity, while revealing a distinct cooperativity between their functions. Strikingly, FOSL1 plays different roles in human and mouse and FOSL-mediated Th17 regulation is opposed by the AP-1 factor, BATF. Genome-wide occupancy analysis demonstrated the co-localization of FOSL1, FOSL2 and BATF in the vicinity of key Th17 genes. The functional interplay among these factors is possibly governed by sharing interactions with a common set of lineage-associated proteins. We further discovered that the genomic binding sites of these factors harbour a large number of disease-linked SNPs, many of which alter the ability of a given factor to bind DNA. Our findings thus provide crucial insights into the transcriptional regulation of human Th17 function and associated pathologies. ONE SENTENCE SUMMARYFOSL1- and FOSL2-mediated transcription during early human Th17 differentiation

immunology↗