Amino Acid Pools and the Role of PheRS in the Fidelity of Translation

Translation is a highly accurate process with an overall error rate of only about 10-4. The fidelity of translation is determined by two main events: synthesis of cognate amino acid:tRNA pairs by aminoacyl-tRNA synthetases (aaRSs) and accurate selection of aminoacyl-tRNAs (aa-tRNAs) by the ribosome. To ensure correct pairing between amino acids and tRNA molecules, some aminoacyl-tRNA synthetases (aaRSs) possess editing mechanisms, whereby non-cognate amino acids can be hydrolyzed, thereby preventing the incorrect amino acid from being transferred to the ribosome and incorporated into the polypeptide chain. Such editing abilities augment the fidelity of the translation machinery. To correct errors occurring in amino acid selection, phenylalanyl-tRNA synthetase (PheRS) possesses a post-transfer editing activity, which targets misacylated Tyr-tRNAPhe. Although the mechanism of hydrolysis of Tyr-tRNAPhe has been examined, the impact of editing at the cellular level remains unclear; however, editing may be especially important when cells are experiencing physiological stress and/or when the relative concentration of tyrosine is elevated. To investigate these issues, the growth of four mutant strains of Escherichia coli was examined. To do so, the strains were grown under a set of four different conditions with varying concentrations of phenylalanine and tyrosine, and growth curves were established and analyzed. The implications of this study are relevant to understanding the survival strategies of pathogens in limiting environments and to understanding diseases which result from errors in editing pathways. Future work in this area may include quantifying intracellular amino acid pools to better understand their impact on the quality control of translation.Dean's Undergraduate Research Fund AwardNo embarg

Relationship of cardiovascular disease risk and hearing loss in a clinical population

Abstract Hearing loss has been associated with individual cardiovascular disease (CVD) risk factors and, to a lesser extent, CVD risk metrics. However, these relationships are understudied in clinical populations. We conducted a retrospective study of electronic health records to evaluate the relationship between hearing loss and CVD risk burden. Hearing loss was defined as puretone average (PTA0.5,1,2,4) > 20 dB hearing level (HL). Optimal CVD risk was defined as nondiabetic, nonsmoking, systolic blood pressure (SBP) < 120 and diastolic (D)BP < 80 mm Hg, and total cholesterol < 180 mg/dL. Major CVD risk factors were diabetes, smoking, hypertension, and total cholesterol ≥ 240 mg/dL or statin use. We identified 6332 patients (mean age = 62.96 years; 45.5% male); 64.0% had hearing loss. Sex-stratified logistic regression adjusted for age, noise exposure, hearing aid use, and body mass index examined associations between hearing loss and CVD risk. For males, diabetes, hypertension, smoking, and ≥ 2 major CVD risk factors were associated with hearing loss. For females, diabetes, smoking, and ≥ 2 major CVD risk factors were significant risk factors. Compared to those with no CVD risk factors, there is a higher likelihood of hearing loss in patients with ≥ 2 major CVD risk factors. Future research to better understand sex dependence in the hearing loss-hypertension relationship is indicated

mtDNA diversity in azara's owl monkeys (Aotus azarai azarai) of the Argentinean Chaco

Owl monkeys (Aotus spp.) inhabit much of South America yet represent an enigmatic evolutionary branch among primates. While morphological, cytogenetic, and immunological evidence suggest that owl monkey populations have undergone isolation and diversification since their emergence in the New World, problems with adjacent species ranges, and sample provenance have complicated efforts to characterize genetic variation within the genus. As a result, the phylogeographic history of owl monkey species and subspecies remains unclear, and the extent of genetic diversity at the population level is unknown. To explore these issues, we analyzed mitochondrial DNA (mt DNA) variation in a population of wild Azara's owl monkeys (Aotus azarai azarai) living in the Gran Chaco region of Argentina. We sequenced the complete mitochondrial genome from one individual (16,585 base pairs (bp)) and analyzed 1,099 bp of the hypervariable control region (CR) and 696 bp of the cytochrome oxidase II (COII) gene in 117 others. In addition, we sequenced the mitochondrial genome (16,472 bp) of one Nancy Ma's owl monkey (A. nancymaae). Based on the whole mtDNA and COII data, we observed an ancient phylogeographic discontinuity among Aotus species living north, south, and west of the Amazon River that began more than eight million years ago. Our population analyses identified three major CR lineages and detected a high level of haplotypic diversity within A. a. azarai. These data point to a recent expansion of Azara's owl monkeys into the Argentinean Chaco. Overall, we provide a detailed view of owl monkey mtDNA variation at genus, species, and population levels.Fil: Babb, Paul L.. University of Pennsylvania; Estados UnidosFil: Fernandez Duque, Eduardo. University of Pennsylvania; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Baiduc, Caitlin A.. University of Pennsylvania; Estados UnidosFil: Gagneux, Pascal. University of California at San Diego; Estados Unidos. Center for Academic Research and Training in Anthropogeny; Estados UnidosFil: Evans, Sian. DuMond Conservancy for Primates and Tropical Forests, Miami; Estados UnidosFil: Schurr, Theodore. University of Pennsylvania; Estados Unido

Chimeric antigen receptors enable superior control of HIV replication by rapidly killing infected cells.

Engineered T cells hold great promise to become part of an effective HIV cure strategy, but it is currently unclear how best to redirect T cells to target HIV. To gain insight, we generated engineered T cells using lentiviral vectors encoding one of three distinct HIV-specific T cell receptors (TCRs) or a previously optimized HIV-targeting chimeric antigen receptor (CAR) and compared their functional capabilities. All engineered T cells had robust, antigen-specific polyfunctional cytokine profiles when mixed with artificial antigen-presenting cells. However, only the CAR T cells could potently control HIV replication. TCR affinity enhancement did not augment HIV control but did allow TCR T cells to recognize common HIV escape variants. Interestingly, either altering Nef activity or adding additional target epitopes into the HIV genome bolstered TCR T cell anti-HIV activity, but CAR T cells remained superior in their ability to control HIV replication. To better understand why CAR T cells control HIV replication better than TCR T cells, we performed a time course to determine when HIV-specific T cells were first able to activate Caspase 3 in HIV-infected targets. We demonstrated that CAR T cells recognized and killed HIV-infected targets more rapidly than TCR T cells, which correlates with their ability to control HIV replication. These studies suggest that the speed of target recognition and killing is a key determinant of whether engineered T cell therapies will be effective against infectious diseases