Hyperconnectivity of neuronal circuits due to increased synaptic protein synthesis is postulated to cause Autism Spectrum Disorders (ASD). The mammalian target of rapamycin (mTOR) is strongly implicated in ASD via upstream signaling. However, downstream regulatory mechanisms are ill-defined. We show that knockout (KO) of the eukaryotic translation Initiation Factor 4E-Binding Protein 2 (4E-BP2), an eIF4E-repressor downstream of mTOR, or eIF4E overexpression lead to increased translation of neuroligins, which are post-synaptic proteins that are causally linked to ASD. 4E-BP2-KO mice exhibit an increased ratio of excitatory to inhibitory synaptic inputs and autistic-like behaviors: social interaction deficits, altered communication and repetitive/stereotyped behaviors. Pharmacological inhibition of eIF4E activity or normalization of neuroligin 1, but not neuroligin 2 protein amounts, restore the normal excitation/inhibition ratio and rectify the social behavior deficits. Thus, translational control by eIF4E regulates the synthesis of neuroligins, maintaining the excitation to inhibition balance, and its dysregulation engenders ASD-like phenotypes.

Tandem stretches of guanines can associate in hydrogen-bonded arrays to form G-quadruplexes, which are stabilized by K+ ions. Using computational methods, we searched for G-Quadruplex Sequence (GQS) patterns in the model plant species Arabidopsis thaliana. We found ∼1200 GQS with a G3 repeat sequence motif, most of which are located in the intergenic region. Using a Markov modeled genome, we determined that GQS are significantly underrepresented in the genome. Additionally, we found ∼43 000 GQS with a G2 repeat sequence motif; notably, 80% of these were located in genic regions, suggesting that these sequences may fold at the RNA level. Gene Ontology functional analysis revealed that GQS are overrepresented in genes encoding proteins of certain functional categories, including enzyme activity. Conversely, GQS are underrepresented in other categories of genes, notably those for non-coding RNAs such as tRNAs and rRNAs. We also find that genes that are differentially regulated by drought are significantly more likely to contain a GQS. CD-detected K+ titrations performed on representative RNAs verified formation of quadruplexes at physiological K+ concentrations. Overall, this study indicates that GQS are present at unique locations in Arabidopsis and that folding of RNA GQS may play important roles in regulating gene expression.

The genomic RNA ofpotyviruses has a characteristic 5' non-translated region (5'NTR) to which a viral protein, VPg, is covalently attached. This suggests that the viral RNA lacks a conventional cap structure and thus its translation may not proceed in the same way as most cellular mRNAs. To investigate the role of the 5'NTR during translation, various derivatives of the turnip mosaic potyvirus (TuMV) leader were fused to the reporter gene fl-glucuronidase (GUS). These constructs were used to monitor the efficiency of translation in vitro in a rabbit reticulocyte lysate and in planta following microprojectile DNA delivery into tobacco cell suspensions. GUS transcripts fused with the TuMV 5'NTR, whether they were capped or not, were efficiently translated, whereas GUS transcripts without the viral leader needed to be capped for expression. When transcripts of the viral leader were supplied in excess over functional transcripts, translation was inhibited in a dose-dependent manner. Similarly, transcripts synthesized from the reverse complement of the 5'NTR inhibited translation to the same extent as the wild-type sequence, indicating that cap independence was not conferred by a specific sequence within the viral leader. A stable hairpin loop was placed in front or after the viral sequence. This hairpin loop normally prevented translation of control GUS transcripts but when the viral leader was positioned after it a significant level of GUS activity was measured, whether the transcripts were capped or not. On the other hand, when the hairpin loop was positioned after the viral leader, no GUS activity was measured. These results suggested that ribosomes bound to an internal site within the TuMV 5'NTR and then presumably scanned the sequence for the initiator AUG.

Signaling diversity of G protein-coupled (GPCR) ligands provides novel opportunities to develop more effective, better-tolerated therapeutics. Taking advantage of these opportunities requires identifying which effectors should be specifically activated or avoided so as to promote desired clinical responses and avoid side effects. However, identifying signaling profiles that support desired clinical outcomes remains challenging. This study describes signaling diversity of mu opioid receptor (MOR) ligands in terms of logistic and operational parameters for ten different in vitro readouts. It then uses unsupervised clustering of curve parameters to: classify MOR ligands according to similarities in type and magnitude of response, associate resulting ligand categories with frequency of undesired events reported to the pharmacovigilance program of the Food and Drug Administration and associate signals to side effects. The ability of the classification method to associate specific in vitro signaling profiles to clinically relevant responses was corroborated using β2-adrenergic receptor ligands.