Biology subjects

Chesarino, N. M.

Publications and source records attributed to Chesarino, N. M..

5 recordsLinked to original sources

bioRxiv2026

Structural Adaptability in HIV-2 Vif Drives Broad Antagonism of APOBEC3G

APOBEC3G (A3G), a restriction factor, is a barrier for zoonosis and targeted for degradation by the lentiviral protein Vif. Human Immunodeficiency Virus Type 1 (HIV-1) and HIV-2 arose from transmissions of lentiviruses from Old World monkeys to hominid primates. While HIV-1 Vif needed to adapt to specific residues in the arms race interface with A3G, HIV-2 Vif has greater tolerance for diversity there. Here, our cryo-EM structure of HIV-2 Vif and human A3G allows us to explore the mechanism underlying HIV-2 Vif broad specificity. While HIV-2 Vif does bind the arms race interface on A3G, HIV-2 Vif encodes tryptophans with low backbone stability to engage another interface on A3G. We propose a model where flexible loops in HIV-2 Vif undergo conformational selection to recognize diverse A3Gs, whereas the equivalent loops in HIV-1 Vif are preorganized to bind hA3G.

biophysics↗

bioRxiv2026

Productive Mayaro Virus Infection Requires Host Fatty Acid Synthase for nsP1 S-palmitoylation

To date, twenty-seven pathogenic human viruses require host-catalyzed de novo fatty acid biosynthesis for replication. This pathway is driven by fatty acid synthase (FASN), which produces palmitate. Palmitate is a precursor for various functions during viral infection, including lipid droplet formation for assembly, beta-oxidation for ATP generation, and post-translational modification of proteins. Whether Mayaro virus (MAYV), an emerging alphavirus that causes debilitating arthritogenic disease, required FASN for infection was unknown. Using genetic and pharmacological approaches in a human cell line and primary cell model, we found that MAYV requires FASN-dependent palmitate synthesis for virion production. To determine how palmitate contributes to infection, we pharmacologically inhibited pathways downstream of FASN and found that only 2-bromopalmitate (2-BP), a protein palmitoylation inhibitor, led to a 94% reduction in MAYV infection. S-palmitoylation is a post-translational modification in which palmitate is attached to sulfur atoms in cysteine residues. In chikungunya virus, a related alphavirus, FASN-dependent palmitoylation of nonstructural protein 1 (nsP1) is essential for membrane association and replication. Consequently, we hypothesized that MAYV nsP1 is palmitoylated in a FASN-dependent manner. Using an alkyne acetate analog, Alk-4, metabolized by FASN into alkyne palmitate, we observed specific labeling of wild-type nsP1 at conserved cysteine residues (C417-419), but not of a cysteine-to-alanine triple mutant. Treatment with TVB-2640 or 2-BP abrogated Alk-4 labeling of wild-type nsP1 during active infection, reinforcing that MAYV protein palmitoylation is a FASN-dependent process. Our findings reveal a conserved mechanism of FASN-dependent protein palmitoylation in alphaviruses and highlight FASN as a potential anti-viral target. ImportanceMayaro virus (MAYV) is a neglected, mosquito-borne tropical virus that causes debilitating pathologies, such as chronic joint pain that can last from months to years. Currently, MAYV transmissions are endemic in sylvatic and peri-urban regions in Central and South America and the Caribbean. However, MAYV has been detected in urban-adapted mosquitos like Aedes aegypti (Ae. aegypti) and is a concern for potential global spread. Consequently, investigating the mechanisms of MAYV infection is critical to uncover opportunities for antiviral drug development. In this study, we report that MAYV infection requires host fatty acid synthase (FASN) derived palmitate for palmitoylation of the viral non-structural protein 1 (nsP1). In addition, we report that inhibiting FASN with the clinically advanced small molecule TVB-2640 significantly reduced MAYV infection and nsP1 palmitoylation. This study highlights FASN as an essential host factor for MAYV replication and establishes it as a promising therapeutic target for MAYV and related alphaviruses.

microbiology↗

bioRxiv2021

HIV-1 Vif gained breadth in APOBEC3G specificity after cross-species transmission of its precursors

APOBEC3G (A3G) is a host-encoded cytidine deaminase that potently restricts retroviruses, such as HIV-1, and depends on its ability to package into virions. As a consequence of this, HIV-1 protein Vif has evolved to antagonize human A3G by targeting it for ubiquitination and subsequent degradation. There is an ancient arms-race between Vif and A3G highlighted by amino acids 128 and 130 in A3G that have evolved under positive selection due to Vif-mediated selective pressure in Old World primates. Nonetheless, not all possible amino acid combinations at these sites have been sampled by nature and it is not clear the evolutionary potential of species to resist Vif antagonism. To explore the evolutionary space of positively selected sites in the Vif-binding region of A3G, we designed a combinatorial mutagenesis screen to introduce all 20 amino acids at sites 128 and 130. Our screen uncovered mutants of A3G with several interesting phenotypes, including loss of stability and resistance of Vif antagonism. However, HIV-1 Vif exhibited remarkable flexibility in antagonizing A3G 128 and 130 mutants, which significantly reduces viable Vif resistance strategies for hominid primates. Importantly, we find that broadened Vif specificity was conferred through Loop 5 adaptations that were required for cross-species adaptation from Old World monkey A3G to hominid A3G. Our evidence suggests that Vif adaptation to novel A3G interfaces during cross-species transmission may train Vif towards broadened specificity that can further facilitate cross-species transmissions and raise the barrier to host resistance.

evolutionary biology↗

bioRxiv2020

Polymorphisms in human APOBEC3H differentially regulate ubiquitination and antiviral activity

The APOBEC3 family of cytidine deaminases are an important part of the host innate immune defense against endogenous retroelements and retroviruses like human immunodeficiency virus (HIV). APOBEC3H (A3H) is the most polymorphic of the human APOBEC3 genes, with four major haplotypes circulating in the population. Haplotype II is the only antivirally-active variant of A3H, while the majority of the population possess independently destabilizing polymorphisms present in haplotype I (R105G) and haplotypes III and IV (N15del). Here, we show that instability introduced by either polymorphism is positively correlated with degradative ubiquitination, while haplotype II is protected from this modification. Inhibiting ubiquitination by mutating all of the A3H lysines increased expression of haplotypes III and IV, but these stabilized forms of haplotype III and IV had a strict nuclear localization, and did not incorporate into virions, nor exhibit antiviral activity, thus separating stabilization from function. On the other hand, the instability and functional deficiencies of haplotype III could be rescued by fusion to haplotype II, supporting a model by which antiviral A3H is actively stabilized through a cytoplasmic retention mechanism. Thus, the evolutionary loss of A3H activity in many humans involves functional deficiencies independent of protein stability.

microbiology↗

bioRxiv2019

IFITM3 protects the heart during influenza virus infection

Influenza virus primarily targets the lungs, but dissemination and damage to heart tissue is also known to occur in severe infections. Despite this knowledge, influenza virus-induced cardiac pathogenesis and its underlying mechanisms have been difficult to study due to a lack of small animal models. In humans, polymorphisms in the gene encoding interferon-induced transmembrane protein 3 (IFITM3), an antiviral restriction factor, are associated with susceptibility to severe influenza, but whether IFITM3 deficiencies contribute to other aspects of pathogenesis, including cardiac dysfunction, is unknown. We now show that IFITM3 deficiency in a newly generated knockout (KO) mouse model exacerbates illness and mortality following influenza A virus infection. Enhanced pathogenesis correlated with increased replication of virus in the lungs, spleens, and hearts of KO mice relative to wildtype (WT) mice. IFITM3 KO mice exhibited normal cardiac function at baseline, but developed severely aberrant electrical activity upon infection, including decreased heart rate and irregular, arrhythmic RR (interbeat) intervals. In contrast, WT mice exhibited a mild decrease in heart rate without irregularity of RR intervals. Heightened cardiac virus titers and electrical dysfunction in KO animals was accompanied by increased activation of fibrotic pathways and fibrotic lesions in the heart. Our findings reveal an essential role for IFITM3 in controlling influenza virus replication and pathogenesis in heart tissue and establish IFITM3 KO mice as a powerful model to study virus-induced cardiac dysfunction.

immunology↗