48 research outputs found

    Positive Selection and Increased Antiviral Activity Associated with the PARP-Containing Isoform of Human Zinc-Finger Antiviral Protein

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    Intrinsic immunity relies on specific recognition of viral epitopes to mount a cell-autonomous defense against viral infections. Viral recognition determinants in intrinsic immunity genes are expected to evolve rapidly as host genes adapt to changing viruses, resulting in a signature of adaptive evolution. Zinc-finger antiviral protein (ZAP) from rats was discovered to be an intrinsic immunity gene that can restrict murine leukemia virus, and certain alphaviruses and filoviruses. Here, we used an approach combining molecular evolution and cellular infectivity assays to address whether ZAP also acts as a restriction factor in primates, and to pinpoint which protein domains may directly interact with the virus. We find that ZAP has evolved under positive selection throughout primate evolution. Recurrent positive selection is only found in the poly(ADP-ribose) polymerase (PARP)–like domain present in a longer human ZAP isoform. This PARP-like domain was not present in the previously identified and tested rat ZAP gene. Using infectivity assays, we found that the longer isoform of ZAP that contains the PARP-like domain is a stronger suppressor of murine leukemia virus expression and Semliki forest virus infection. Our study thus finds that human ZAP encodes a potent antiviral activity against alphaviruses. The striking congruence between our evolutionary predictions and cellular infectivity assays strongly validates such a combined approach to study intrinsic immunity genes

    Diversifying selection and functional analysis of interleukin-4 suggests antagonism-driven evolution at receptor-binding interfaces

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    <p>Abstract</p> <p>Background</p> <p>Interleukin-4 (IL4) is a secreted immunoregulatory cytokine critically involved in host protection from parasitic helminths <abbrgrp><abbr bid="B1">1</abbr></abbrgrp>. Reasoning that helminths may have evolved mechanisms to antagonize IL4 to maximize their dispersal, we explored mammalian IL4 evolution.</p> <p>Results</p> <p>This analysis revealed evidence of diversifying selection at 15 residues, clustered in epitopes responsible for IL4 binding to its Type I and Type II receptors. Such a striking signature of selective pressure suggested either recurrent episodes of pathogen antagonism or ligand/receptor co-evolution. To test the latter possibility, we performed detailed functional analysis of IL4 allotypes expressed by <it>Mus musculus musculus </it>and <it>Mus musculus castaneus</it>, which happen to differ at 5 residues (including three at positively selected sites) in and adjacent to the site 1 epitope that binds the IL4Rα subunit shared by the Type I and Type II IL4 receptors. We show that this intra-species variation affects the ability of IL4 neither to bind IL4 receptor alpha (IL4Rα) nor to signal biological responses through its Type I receptor.</p> <p>Conclusions</p> <p>Our results -- reminiscent of clustered positively selected sites revealing functionally important residues at host-virus interaction interfaces -- are consistent with IL4 having evolved to avoid recurrent pathogen antagonism, while maintaining the capacity to bind and signal through its cognate receptor. This work exposes what may be a general feature of evolutionary conflicts fought by pathogen antagonists at host protein-protein interaction interfaces involved in immune signaling: the emergence of receptor-binding ligand epitopes capable of buffering amino acid variation.</p

    Use of Sperm In Vitro Capacitation and Flow Cytometry to Estimate Bull Fertility

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    Study Description: Frozen-thawed semen from five bulls previously identified as high (48.1% and 47.7%, bulls A and B, respectively), intermediary (45.5%, bull C) or low (43.1% and 40.7%, bulls D and E, respectively) fertility, based on pregnancy per AI, were evaluated with several laboratory measures. Measures included total motility, sperm plasma membrane integrity (viability), acrosome integrity, reactive oxygen species (ROS), mitochondrial membrane energy potential (mito-potential), zinc signatures (signatures 1 to 4), and CD9 protein populations at pre-wash, post-wash, h 0 (diluted with non-capacitation media), and at 0, 3, 6, and 24 h after dilution with capacitation media and incubation at 37 ºC. Data were analyzed using the GLIMMIX procedure of SAS for repeated measures with bull, time, and the interaction as fixed effects. Bull by time interaction was significant (P ≤ 0.01) for total motility and viability. There tended (P = 0.06) to be a bull by time interaction for zinc signatures 1 + 2 combined. There was a significant effect of bull (P ≤ 0.03) for viability, viable sperm with disrupted acrosome, zinc signatures 1, 2, and 1 + 2, viable CD9- (CD9 negative), and dead CD9+ (CD9 positive). High and intermediary field fertility bulls had greater (P ≤ 0.04) percentages of viable sperm, zinc signature 2, and zinc signature 1 + 2 compared to low fertility bulls. High and intermediary fertility bulls had decreased (P ≤ 0.05) percentage of dead CD9+ compared to low fertility bulls. There was or tended to be a positive correlation between pregnancy per AI and viability (P = 0.10; r = 0.81), zinc signature 2 (P = 0.04; r = 0.89), and zinc signature 1 + 2 (P = 0.10; r = 0.80)

    Parps: Rapidly Evolving Weapons in the War against Viral Infection

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    Post-translational protein modifications such as phosphorylation and ubiquitinylation are common molecular targets of conflict between viruses and their hosts. However, the role of other post-translational modifications, such as ADP-ribosylation, in host-virus interactions is less well characterized. ADP-ribosylation is carried out by proteins encoded by the PARP (also called ARTD) gene family. The majority of the 17 human PARP genes are poorly characterized. However, one PARP protein, PARP13/ZAP, has broad antiviral activity and has evolved under positive (diversifying) selection in primates. Such evolution is typical of domains that are locked in antagonistic 'arms races' with viral factors. To identify additional PARP genes that may be involved in host-virus interactions, we performed evolutionary analyses on all primate PARP genes to search for signatures of rapid evolution. Contrary to expectations that most PARP genes are involved in 'housekeeping' functions, we found that nearly one-third of PARP genes are evolving under strong recurrent positive selection. We identified a >300 amino acid disordered region of PARP4, a component of cytoplasmic vault structures, to be rapidly evolving in several mammalian lineages, suggesting this region serves as an important host-pathogen specificity interface. We also found positive selection of PARP9, 14 and 15, the only three human genes that contain both PARP domains and macrodomains. Macrodomains uniquely recognize, and in some cases can reverse, protein mono-ADP-ribosylation, and we observed strong signatures of recurrent positive selection throughout the macro-PARP macrodomains. Furthermore, PARP14 and PARP15 have undergone repeated rounds of gene birth and loss during vertebrate evolution, consistent with recurrent gene innovation. Together with previous studies that implicated several PARPs in immunity, as well as those that demonstrated a role for virally encoded macrodomains in host immune evasion, our evolutionary analyses suggest that addition, recognition and removal of ADP-ribosylation is a critical, underappreciated currency in host-virus conflicts

    Pest population dynamics are related to a continental overwintering gradient

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    Overwintering success is an important determinant of arthropod populations that must be considered as climate change continues to influence the spatiotemporal population dynamics of agricultural pests. Using a long-term monitoring database and biologically relevant overwintering zones, we modeled the annual and seasonal population dynamics of a common pest, Helicoverpa zea (Boddie), based on three overwintering suitability zones throughout North America using four decades of soil temperatures: the southern range (able to persist through winter), transitional zone (uncertain overwintering survivorship), and northern limits (unable to survive winter). Our model indicates H. zea population dynamics are hierarchically structured with continental-level effects that are partitioned into three geographic zones. Seasonal populations were initially detected in the southern range, where they experienced multiple large population peaks. All three zones experienced a final peak between late July (southern range) and mid-August to mid-September (transitional zone and northern limits). The southern range expanded by 3% since 1981 and is projected to increase by twofold by 2099 but the areas of other zones are expected to decrease in the future. These changes suggest larger populations may persist at higher latitudes in the future due to reduced low-temperature lethal events during winter. Because H. zea is a highly migratory pest, predicting when populations accumulate in one region can inform synchronous or lagged population development in other regions. We show the value of combining long-term datasets, remotely sensed data, and laboratory findings to inform forecasting of insect pests
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