Modulation of Escherichia coli Translation by the Specific Inactivation of tRNAGly Under Oxidative Stress

Bacterial oxidative stress responses are generally controlled by transcription factors that modulate the synthesis of RNAs with the aid of some sRNAs that control the stability, and in some cases the translation, of specific mRNAs. Here, we report that oxidative stress additionally leads to inactivation of tRNAGly in Escherichia coli, inducing a series of physiological changes. The observed inactivation of tRNAGly correlated with altered efficiency of translation of Gly codons, suggesting a possible mechanism of translational control of gene expression under oxidative stress. Changes in translation also depended on the availability of glycine, revealing a mechanism whereby bacteria modulate the response to oxidative stress according to the prevailing metabolic state of the cells

Modulation of \u3cem\u3eEscherichia coli\u3c/em\u3e Translation by the Specific Inactivation of tRNA\u3csup\u3eGly\u3c/sup\u3e Under Oxidative Stress

Bacterial oxidative stress responses are generally controlled by transcription factors that modulate the synthesis of RNAs with the aid of some sRNAs that control the stability, and in some cases the translation, of specific mRNAs. Here, we report that oxidative stress additionally leads to inactivation of tRNAGly in Escherichia coli, inducing a series of physiological changes. The observed inactivation of tRNAGly correlated with altered efficiency of translation of Gly codons, suggesting a possible mechanism of translational control of gene expression under oxidative stress. Changes in translation also depended on the availability of glycine, revealing a mechanism whereby bacteria modulate the response to oxidative stress according to the prevailing metabolic state of the cells

Effect of apomorphine on cognitive performance and sensorimotor gating in humans

Contains fulltext : 88792.pdf (publisher's version ) (Closed access)INTRODUCTION: Dysfunction of brain dopamine systems is involved in various neuropsychiatric disorders. Challenge studies with dopamine receptor agonists have been performed to assess dopamine receptor functioning, classically using the release of growth hormone (GH) from the hindbrain as primary outcome measure. The objective of the current study was to assess dopamine receptor functioning at the forebrain level. METHODS: Fifteen healthy male volunteers received apomorphine sublingually (2 mg), subcutaneously (0.005 mg/kg), and placebo in a balanced, double-blind, cross-over design. Outcome measures were plasma GH levels, performance on an AX continuous performance test, and prepulse inhibition of the acoustic startle. The relation between central outcome measures and apomorphine levels observed in plasma and calculated in the brain was modeled using a two-compartmental pharmacokinetic-pharmacodynamic analysis. RESULTS: After administration of apomorphine, plasma GH increased and performance on the AX continuous performance test deteriorated, particularly in participants with low baseline performance. Apomorphine disrupted prepulse inhibition (PPI) on high-intensity (85 dB) prepulse trials and improved PPI on low intensity (75 dB) prepulse trials, particularly in participants with low baseline PPI. High cognitive performance at baseline was associated with reduced baseline sensorimotor gating. Neurophysiological measures correlated best with calculated brain apomorphine levels after subcutaneous administration. CONCLUSION: The apomorphine challenge test appears a useful tool to assess dopamine receptor functioning at the forebrain level. Modulation of the effect of apomorphine by baseline performance levels may be explained by an inverted U-shape relation between prefrontal dopamine functioning and cognitive performance, and mesolimbic dopamine functioning and sensorimotor gating. Future apomorphine challenge tests preferentially use multiple outcome measures, after subcutaneous administration of apomorphine.1 januari 201

Mutations in KEOPS-Complex Genes Cause Nephrotic Syndrome with Primary Microcephaly

Galloway-Mowat syndrome (GAMOS) is an autosomal-recessive disease characterized by the combination of early-onset nephrotic syndrome (SRNS) and microcephaly with brain anomalies. Here we identified recessive mutations in OSGEP, TP53RK, TPRKB, and LAGE3, genes encoding the four subunits of the KEOPS complex, in 37 individuals from 32 families with GAMOS. CRISPR-Cas9 knockout in zebrafish and mice recapitulated the human phenotype of primary microcephaly and resulted in early lethality. Knockdown of OSGEP, TP53RK, or TPRKB inhibited cell proliferation, which human mutations did not rescue. Furthermore, knockdown of these genes impaired protein translation, caused endoplasmic reticulum stress, activated DNA-damage-response signaling, and ultimately induced apoptosis. Knockdown of OSGEP or TP53RK induced defects in the actin cytoskeleton and decreased the migration rate of human podocytes, an established intermediate phenotype of SRNS. We thus identified four new monogenic causes of GAMOS, describe a link between KEOPS function and human disease, and delineate potential pathogenic mechanisms

Molecular basis for the bifunctional Uba4–Urm1 sulfur‐relay system in tRNA thiolation and ubiquitin‐like conjugation

The chemical modification of tRNA bases by sulfur is crucial to tune translation and to optimize protein synthesis. In eukaryotes, the ubiquitin-related modifier 1 (Urm1) pathway is responsible for the synthesis of 2-thiolated wobble uridine (U34 ). During the key step of the modification cascade, the E1-like activating enzyme ubiquitin-like protein activator 4 (Uba4) first adenylates and thiocarboxylates the C-terminus of its substrate Urm1. Subsequently, activated thiocarboxylated Urm1 (Urm1-COSH) can serve as a sulfur donor for specific tRNA thiolases or participate in ubiquitin-like conjugation reactions. Structural and mechanistic details of Uba4 and Urm1 have remained elusive but are key to understand the evolutionary branch point between ubiquitin-like proteins (UBL) and sulfur-relay systems. Here, we report the crystal structures of full-length Uba4 and its heterodimeric complex with its substrate Urm1. We show how the two domains of Uba4 orchestrate recognition, binding, and thiocarboxylation of the C-terminus of Urm1. Finally, we uncover how the catalytic domains of Uba4 communicate efficiently during the reaction cycle and identify a mechanism that enables Uba4 to protect itself against self-conjugation with its own product, namely activated Urm1-COSH

A highly conserved tRNA modification contributes to C. albicans filamentation and virulence.

tRNA modifications play important roles in maintaining translation accuracy in all domains of life. Disruptions in the tRNA modification machinery, especially of the anticodon stem loop, can be lethal for many bacteria and lead to a broad range of phenotypes in baker's yeast. Very little is known about the function of tRNA modifications in host-pathogen interactions, where rapidly changing environments and stresses require fast adaptations. We found that two closely related fungal pathogens of humans, the highly pathogenic Candida albicans and its much less pathogenic sister species, Candida dubliniensis, differ in the function of a tRNA-modifying enzyme. This enzyme, Hma1, exhibits species-specific effects on the ability of the two fungi to grow in the hypha morphology, which is central to their virulence potential. We show that Hma1 has tRNA-threonylcarbamoyladenosine dehydratase activity, and its deletion alters ribosome occupancy, especially at 37°C-the body temperature of the human host. A C. albicans HMA1 deletion mutant also shows defects in adhesion to and invasion into human epithelial cells and shows reduced virulence in a fungal infection model. This links tRNA modifications to host-induced filamentation and virulence of one of the most important fungal pathogens of humans.IMPORTANCEFungal infections are on the rise worldwide, and their global burden on human life and health is frequently underestimated. Among them, the human commensal and opportunistic pathogen, Candida albicans, is one of the major causative agents of severe infections. Its virulence is closely linked to its ability to change morphologies from yeasts to hyphae. Here, this ability is linked-to our knowledge for the first time-to modifications of tRNA and translational efficiency. One tRNA-modifying enzyme, Hma1, plays a specific role in C. albicans and its ability to invade the host. This adds a so-far unknown layer of regulation to the fungal virulence program and offers new potential therapeutic targets to fight fungal infections