Jenningsdoyle2400

Synthetic peptides are attractive candidates to manipulate protein-protein interactions inside the cell as they mimic natural interactions to compete for binding. However, protein-peptide interactions are often dynamic and weak. A challenge is to design peptides that make improved interactions with the target. Here, we devise a fragment-linking strategy-"mash-up" design-to deliver a high-affinity ligand, KinTag, for the kinesin-1 motor. Using structural insights from natural micromolar-affinity cargo-adaptor ligands, we have identified and combined key binding features in a single, high-affinity ligand. An X-ray crystal structure demonstrates interactions as designed and reveals only a modest increase in interface area. Moreover, when genetically encoded, KinTag promotes transport of lysosomes with higher efficiency than natural sequences, revealing a direct link between motor-adaptor binding affinity and organelle transport. Together, these data demonstrate a fragment-linking strategy for peptide design and its application in a synthetic motor ligand to direct cellular cargo transport.Viral infection in early pregnancy is a major cause of microcephaly. However, how distinct viruses impair human brain development remains poorly understood. Here we use human brain organoids to study the mechanisms underlying microcephaly caused by Zika virus (ZIKV) and herpes simplex virus (HSV-1). We find that both viruses efficiently replicate in brain organoids and attenuate their growth by causing cell death. However, transcriptional profiling reveals that ZIKV and HSV-1 elicit distinct cellular responses and that HSV-1 uniquely impairs neuroepithelial identity. Furthermore, we demonstrate that, although both viruses fail to potently induce the type I interferon system, the organoid defects caused by their infection can be rescued by distinct type I interferons. These phenotypes are not seen in 2D cultures, highlighting the superiority of brain organoids in modeling viral infections. These results uncover virus-specific mechanisms and complex cellular immune defenses associated with virus-induced microcephaly.Toxin-antitoxin (TA) systems are widespread in bacteria, but their activation mechanisms and bona fide targets remain largely unknown. Here, we characterize a type III TA system, toxIN, that protects E. coli against multiple bacteriophages, including T4. Using RNA sequencing, we find that the endoribonuclease ToxN is activated following T4 infection and blocks phage development primarily by cleaving viral mRNAs and inhibiting their translation. ToxN activation arises from T4-induced shutoff of host transcription, specifically of toxIN, leading to loss of the intrinsically unstable toxI antitoxin. Transcriptional shutoff is necessary and sufficient for ToxN activation. Notably, toxIN does not strongly protect against another phage, T7, which incompletely blocks host transcription. Thus, our results reveal a critical trade-off in blocking host transcription it helps phage commandeer host resources but can activate potent defense systems. More generally, our results now reveal the native targets of an RNase toxin and activation mechanism of a phage-defensive TA system.mRNA translation is coupled to multiprotein complex assembly in the cytoplasm or to protein delivery into intracellular compartments. Here, by combining systematic RNA immunoprecipitation and single-molecule RNA imaging in yeast, we have provided a complete depiction of the co-translational events involved in the biogenesis of a large multiprotein assembly, the nuclear pore complex (NPC). We report that binary interactions between NPC subunits can be established during translation, in the cytoplasm. Strikingly, the nucleoporins Nup1/Nup2, together with a number of nuclear proteins, are instead translated at nuclear pores, through a mechanism involving interactions between their nascent N-termini and nuclear transport receptors. Uncoupling this co-translational recruitment further triggers the formation of cytoplasmic foci of unassembled polypeptides. Ropsacitinib price Altogether, our data reveal that distinct, spatially segregated modes of co-translational interactions foster the ordered assembly of NPC subunits and that localized translation can ensure the proper delivery of proteins to the pore and the nucleus.Activation of the STAT5 transcription factor downstream of the Interleukin-2 receptor (IL-2R) induces expression of Foxp3, a critical step in the differentiation of regulatory T (Treg) cells. Due to the pleiotropic effects of IL-2R signaling, it is unclear how STAT5 acts directly on the Foxp3 locus to promote its expression. Here, we report that IL-2 - STAT5 signaling converged on an enhancer (CNS0) during Foxp3 induction. CNS0 facilitated the IL-2 dependent CD25+Foxp3- precursor to Treg cell transition in the thymus. Its deficiency resulted in impaired Treg cell generation in neonates, which was partially mitigated with age. While the thymic Treg cell paucity caused by CNS0 deficiency did not result in autoimmunity on its own, it exacerbated autoimmune manifestations caused by disruption of the Aire gene. Thus, CNS0 enhancer activity ensures robust Treg cell differentiation early in postnatal life and cooperatively with other tolerance mechanisms minimizes autoimmunity.Adapting to changing environmental conditions requires a prospective inference of future actions and their consequences, a strategy also known as model-based decision making.1-3 In stable environments, extensive experience of actions and their consequences leads to a shift from a model-based to a model-free strategy, whereby behavioral selection is primarily governed by retrospective experiences of positive and negative outcomes. Human and animal studies, where subjects are required to speculate about implicit information and adjust behavioral responses over multiple sessions, point to a role for the central serotonergic system in model-based decision making.4-8 However, to directly test a causal relationship between serotonergic activity and model-based decision making, phase-specific manipulation of serotonergic activity is needed in a one-shot test, where learning by trial and error is neutralized. Moreover, the serotonergic origin responsible for this effect is yet to be determined. Herein, we demonstrate that optogenetic silencing of serotonin neurons in the dorsal raphe nucleus, but not in the median raphe nucleus, disrupts model-based decision making in lithium-induced outcome devaluation tasks.