Tunable quantum interferometer for correlated moiré electrons.

Magic-angle twisted bilayer graphene can host a variety of gate-tunable correlated states - including superconducting and correlated insulator states. Recently, junction-based superconducting moiré devices have been introduced, enabling the study of the charge, spin and orbital nature of superconductivity, as well as the coherence of moiré electrons in magic-angle twisted bilayer graphene. Complementary fundamental coherence effects-in particular, the Little-Parks effect in a superconducting ring and the Aharonov-Bohm effect in a normally conducting ring - have not yet been reported in moiré devices. Here, we observe both phenomena in a single gate-defined ring device, where we can embed a superconducting or normally conducting ring in a correlated or band insulator. The Little-Parks effect is seen in the superconducting phase diagram as a function of density and magnetic field, confirming the effective charge of 2e. We also find that the coherence length of conducting moiré electrons exceeds several microns at 50 mK. In addition, we identify a regime characterized by h/e-periodic oscillations but with superconductor-like nonlinear transport.

Simple, fast and efficient iTOP-mediated delivery of CRISPR/Cas9 RNP in difficult-to-transduce human cells including primary T cells.

The advent of the CRISPR/Cas9 system has transformed the field of human genome engineering and has created new perspectives in the development of innovative cell therapies. However, the absence of a simple, fast and efficient delivery method of CRISPR/Cas9 into primary human cells has been limiting the progress of CRISPR/Cas9-based therapies. Here, we describe an optimized protocol for iTOP-mediated delivery of CRISPR/Cas9 in various human cells, including primary T cells, induced pluripotent stem cells (hiPSCs), Jurkat, ARPE-19 and HEK293 cells. We compare iTOP to other CRISPR/Cas9 delivery methods, such as electroporation and lipofection, and evaluate the corresponding gene-editing efficiencies and post-treatment cell viabilities. We demonstrate that the gene editing achieved by iTOP-mediated delivery of CRISPR/Cas9 is 40-95 % depending on the cell type, while post-iTOP cell viability remains high in the range of 70-95 %. Collectively, we present an optimized workflow for a simple, high-throughput and effective iTOP-mediated delivery of CRISPR/Cas9 to engineer difficult-to-transduce human cells. We believe that the iTOP technology® could contribute to the development of novel CRISPR/Cas9-based cell therapies.

Cysteine oxidation triggers amyloid fibril formation of the tumor suppressor p16INK4A.

The tumor suppressor p16INK4A induces cell cycle arrest and senescence in response to oncogenic transformation and is therefore frequently lost in cancer. p16INK4A is also known to accumulate under conditions of oxidative stress. Thus, we hypothesized it could potentially be regulated by reversible oxidation of cysteines (redox signaling). Here we report that oxidation of the single cysteine in p16INK4A in human cells occurs under relatively mild oxidizing conditions and leads to disulfide-dependent dimerization. p16INK4A is an all α-helical protein, but we find that upon cysteine-dependent dimerization, p16INK4A undergoes a dramatic structural rearrangement and forms aggregates that have the typical features of amyloid fibrils, including binding of diagnostic dyes, presence of cross-ß sheet structure, and typical dimensions found in electron microscopy. p16INK4A amyloid formation abolishes its function as a Cyclin Dependent Kinase 4/6 inhibitor. Collectively, these observations mechanistically link the cellular redox state to the inactivation of p16INK4A through the formation of amyloid fibrils.

Proteome-wide Changes in Protein Turnover Rates in C. elegans Models of Longevity and Age-Related Disease.

The balance between protein synthesis and protein breakdown is a major determinant of protein homeostasis, and loss of protein homeostasis is one of the hallmarks of aging. Here we describe pulsed SILAC-based experiments to estimate proteome-wide turnover rates of individual proteins. We applied this method to determine protein turnover rates in Caenorhabditis elegans models of longevity and Parkinson's disease, using both developing and adult animals. Whereas protein turnover in developing, long-lived daf-2(e1370) worms is about 30% slower than in controls, the opposite was observed in day 5 adult worms, in which protein turnover in the daf-2(e1370) mutant is twice as fast as in controls. In the Parkinson's model, protein turnover is reduced proportionally over the entire proteome, suggesting that the protein homeostasis network has a strong ability to adapt. The findings shed light on the relationship between protein turnover and healthy aging.

Covalent targeting of acquired cysteines in cancer.

The thiolate side chain of cysteine has a unique functionality that drug hunters and chemical biologists have begun to exploit. For example, targeting cysteine residues in the ATP-binding pockets of kinases with thiol-reactive molecules has afforded increased selectivity and potency to drugs like imbrutinib, which inhibits the oncogene BTK, and CO-1686 and AZD9291 that target oncogenic mutant EGFR. Recently, disulfide libraries and targeted GDP-mimetics have been used to selectively label the G12C oncogenic mutation in KRAS. We reasoned that other oncogenes contain mutations to cysteine, and thus screened the Catalog of Somatic Mutations in Cancer for frequently acquired cysteines. Here, we describe the most common mutations and discuss how these mutations could be potential targets for cysteine-directed personalized therapeutics.

The small GTPase RALA controls c-Jun N-terminal kinase-mediated FOXO activation by regulation of a JIP1 scaffold complex.

FOXO (forkhead box O) transcription factors are tumor suppressors and increase the life spans of model organisms. Cellular stress, in particular oxidative stress caused by an increase in levels of reactive oxygen species (ROS), activates FOXOs through JNK-mediated phosphorylation. Importantly, JNK regulation of FOXO is evolutionarily conserved. Here we identified the pathway that mediates ROS-induced JNK-dependent FOXO regulation. Following increased ROS, RALA is activated by the exchange factor RLF (RalGDS-like factor), which is in complex with JIP1 (C-Jun-amino-terminal-interacting protein 1) and JNK. Active RALA consequently regulates assembly and activation of MLK3, MKK4, and JNK onto the JIP1 scaffold. Furthermore, regulation of FOXO by RALA and JIP1 is conserved in C. elegans, where both ral-1 and jip-1 depletion impairs heat shock-induced nuclear translocation of the FOXO orthologue DAF16.

Redox-dependent control of FOXO/DAF-16 by transportin-1.

Forkhead box O (FOXO; DAF-16 in worms) transcription factors, which are of vital importance in cell-cycle control, stress resistance, tumor suppression, and organismal lifespan, are largely regulated through nucleo-cytoplasmic shuttling. Insulin signaling keeps FOXO/DAF-16 cytoplasmic, and hence transcriptionally inactive. Conversely, as in loss of insulin signaling, reactive oxygen species (ROS) can activate FOXO/DAF-16 through nuclear accumulation. How ROS regulate the nuclear translocation of FOXO/DAF-16 is largely unknown. Cysteine oxidation can stabilize protein-protein interactions through the formation of disulfide-bridges when cells encounter ROS. Using a proteome-wide screen that identifies ROS-induced mixed disulfide-dependent complexes, we discovered several interaction partners of FOXO4, one of which is the nuclear import receptor transportin-1. We show that disulfide formation with transportin-1 is required for nuclear localization and the activation of FOXO4/DAF-16 induced by ROS, but not by the loss of insulin signaling. This molecular mechanism for nuclear shuttling is conserved in C. elegans and directly connects redox signaling to the longevity protein FOXO/DAF-16.