Summary Influenza A virus (IAV) is an RNA virus that is cytotoxic to most cell types in which it replicates. IAV activates the host kinase RIPK3, which induces cell death via parallel pathways of necroptosis, driven by the pseudokinase MLKL, and apoptosis, dependent on the adaptor proteins RIPK1 and FADD. How IAV activates RIPK3 remains unknown. We report that DAI (ZBP-1/DLM-1), previously implicated as a cytoplasmic DNA sensor, is essential for RIPK3 activation by IAV. Upon infection, DAI recognizes IAV genomic RNA, associates with RIPK3, and is required for recruitment of MLKL and RIPK1 to RIPK3. Cells lacking DAI or containing DAI mutants deficient in nucleic acid binding are resistant to IAV-triggered necroptosis and apoptosis. DAI-deficient mice fail to control IAV replication and succumb to lethal respiratory infection. These results identify DAI as a link between IAV replication and RIPK3 activation, and implicate DAI as a sensor of RNA viruses.

Background Cisplatin-based neoadjuvant chemotherapy (NAC) before cystectomy is the standard of care for muscle-invasive bladder cancer (MIBC), with 25–50% of patients expected to achieve a pathologic response. Validated biomarkers predictive of response are currently lacking. Objective To discover and validate biomarkers predictive of response to NAC for MIBC. Design, setting, and participants Pretreatment MIBC samples prospectively collected from patients treated in two separate clinical trials of cisplatin-based NAC provided the discovery and validation sets. DNA from pretreatment tumor tissue was sequenced for all coding exons of 287 cancer-related genes and was analyzed for base substitutions, indels, copy number alterations, and selected rearrangements in a Clinical Laboratory Improvements Amendments–certified laboratory. Outcome measurements and statistical analysis The mean number of variants and variant status for each gene were correlated with response. Variant data from the discovery cohort were used to create a classification tree to discriminate responders from nonresponders. The resulting decision rule was then tested in the independent validation set. Results and limitations Patients with a pathologic complete response had more alterations than those with residual tumor in both the discovery (p = 0.024) and validation (p = 0.018) sets. In the discovery set, alteration in one or more of the three DNA repair genes ATM, RB1, and FANCC predicted pathologic response (p < 0.001; 87% sensitivity, 100% specificity) and better overall survival (p = 0.007). This test remained predictive for pathologic response in the validation set (p = 0.033), with a trend towards better overall survival (p = 0.055). These results require further validation in additional sample sets. Conclusions: Genomic alterations in the DNA repair-associated genes ATM, RB1, and FANCC predict response and clinical benefit after cisplatin-based chemotherapy for MIBC. The results suggest that defective DNA repair renders tumors sensitive to cisplatin. Patient summary Chemotherapy given before bladder removal (cystectomy) improves the chance of cure for some but not all patients with muscle-invasive bladder cancer. We found a set of genetic mutations that when present in tumor tissue predict benefit from neoadjuvant chemotherapy, suggesting that testing before chemotherapy may help in selecting patients for whom this approach is recommended.

Interferons (IFNs) are cytokines with powerful immunomodulatory and antiviral properties, but less is known about how they induce cell death. Here, we show that both type I (α/β) and type II (γ) IFNs induce precipitous receptor-interacting protein (RIP)1/RIP3 kinasemediated necrosis when the adaptor protein Fas-associated death domain (FADD) is lost or disabled by phosphorylation, or when caspases (e.g., caspase 8) are inactivated. IFN-induced necrosis proceeds via progressive assembly of a RIP1-RIP3 "necrosome" complex that requires Jak1/STAT1-dependent transcription, but does not need the kinase activity of RIP1. Instead, IFNs transcriptionally activate the RNA-responsive protein kinase PKR, which then interacts with RIP1 to initiate necrosome formation and trigger necrosis. Although IFNs are powerful activators of necrosis when FADD is absent, these cytokines are likely not the dominant inducers of RIP kinase-driven embryonic lethality in FADD-deficient mice. We also identify phosphorylation on serine 191 as a mechanism that disables FADD and collaborates with caspase inactivation to allow IFN-activated necrosis. Collectively, these findings outline a mechanism of IFN-induced RIP kinase-dependent necrotic cell death and identify FADD and caspases as negative regulators of this process.necroptosis | apoptosis I nterferons (IFNs) are pleiotropic cytokines classified into two primary groups, type I (predominantly α/β) and type II (γ). Both classes of IFNs exert their effects via similar Janus kinase (JAK)-signal transducers and activators of transcription (STAT)-dependent signaling cascades to induce the expression of over 500 genes (1). Such IFN-stimulated genes (ISGs) have been reasonably well characterized in the context of antiviral or immune-modulatory signaling, but less is known about how they collaborate to mediate the cytotoxic and antiproliferative effects of IFNs.Recent studies have shed light on a new form of regulated cell death that is activated when caspase-dependent apoptotic pathways are inhibited. This mode of necrotic cell death, sometimes called "necroptosis," requires the serine-threonine kinases receptor-interacting protein 1 (RIP1) and RIP3, and results from overproduction of reactive oxygen species (ROS) and eventual mitochondrial dysfunction (2, 3). Strict negative control of the pronecrotic kinases RIP1 and RIP3 are essential for several aspects of mammalian development and homeostasis, including immune cell proliferation and progression through embryogenesis (4). The proteins FADD, caspase 8, and c-FLIP represent three such negative regulators; in the absence of any of these molecules, the RIP kinases trigger inopportune necrosis, often with severe consequences for the host (4). The core necrosis machinery is thus carefully regulated to execute cell death only in specific contexts, but how this regulation is achieved and which other upstream stimuli exploit RIP kinases to activate necrosis are still relatively poorly described.In the present study, we show that both IFN-γ and IFN-α/β t...

STIM1 and STIM2 are widely expressed endoplasmic reticulum (ER) Ca2+ sensor proteins able to translocate within the ER membrane to physically couple with and gate plasma membrane Orai Ca2+ channels. Although structurally similar, we reveal critical differences in the function of the short STIM-Orai activating regions (SOAR) from STIM1 and STIM2. We narrowed these differences in Orai1 gating to a strategically exposed phenylalanine residue (Phe-394) in SOAR1, which in SOAR2 is substituted by a leucine residue. Remarkably, in full-length STIM1, replacement of Phe-394 with the dimensionally similar but polar histidine headgroup, prevents both Orai1 binding and gating, creating an Orai1 non-agonist. Thus, this residue is critical in tuning the efficacy of Orai activation. While STIM1 is a full Orai1-agonist, leucine-replacement of this crucial residue in STIM2 endows it with partial agonist properties, which may be critical for limiting Orai1 activation stemming from its enhanced sensitivity to store-depletion.

SUMMARY The nuclear lamina is a protein meshwork that lies under the inner nuclear membrane of metazoan cells. One function of the nuclear lamina is to organize heterochromatin at the inner nuclear periphery. However, very little is known about how heterochromatin attaches to the nuclear lamina and how such attachments are restored at mitotic exit. Here we show that a previously unstudied human protein, PRR14, functions to tether heterochromatin to the nuclear periphery during interphase, through associations with heterochromatin protein 1 (HP1) and the nuclear lamina. During early mitosis, PRR14 is released from the nuclear lamina and chromatin, and remains soluble. Strikingly, at the onset of anaphase, PRR14 is incorporated rapidly into chromatin through HP1 binding. Finally, in telophase, PRR14 relocalizes to the reforming nuclear lamina. This stepwise reassembly of PRR14 suggests a novel function in the selection of HP1–bound heterochromatin for reattachment to the nuclear lamina as cells exit mitosis.