KAT2 paralogs prevent dsRNA accumulation and interferon signaling to maintain intestinal stem cells.

Histone acetyltransferases KAT2A and KAT2B are paralogs highly expressed in the intestinal epithelium, but their functions are not well understood. In this study, double knockout of murine Kat2 genes in the intestinal epithelium was lethal, resulting in robust activation of interferon signaling and interferon-associated phenotypes including the loss of intestinal stem cells. Use of pharmacological agents and sterile organoid cultures indicated a cell-intrinsic double-stranded RNA trigger for interferon signaling. Acetyl-proteomics and dsRIP-seq were employed to interrogate the mechanism behind this response, which identified mitochondria-encoded double-stranded RNA as the source of intrinsic interferon signaling. Kat2a and Kat2b therefore play an essential role in regulating mitochondrial functions as well as maintaining intestinal health.

KDM6A Loss Triggers an Epigenetic Switch That Disrupts Urothelial Differentiation and Drives Cell Proliferation in Bladder Cancer.

Disruption of KDM6A, a histone lysine demethylase, is one of the most common somatic alternations in bladder cancer. Insights into how KDM6A mutations affect the epigenetic landscape to promote carcinogenesis could help reveal potential new treatment approaches. Here, we demonstrated that KDM6A loss triggers an epigenetic switch that disrupts urothelial differentiation and induces a neoplastic state characterized by increased cell proliferation. In bladder cancer cells with intact KDM6A, FOXA1 interacted with KDM6A to activate genes instructing urothelial differentiation. KDM6A-deficient cells displayed simultaneous loss of FOXA1 target binding and genome-wide redistribution of the bZIP transcription factor ATF3, which in turn repressed FOXA1-target genes and activated cell-cycle progression genes. Importantly, ATF3 depletion reversed the cell proliferation phenotype induced by KDM6A deficiency. These data establish that KDM6A loss engenders an epigenetic state that drives tumor growth in an ATF3-dependent manner, creating a potentially targetable molecular vulnerability. SIGNIFICANCE: A gain-of-function epigenetic switch that disrupts differentiation is triggered by inactivating KDM6A mutations in bladder cancer and can serve as a potential target for novel therapies.

Reduced nicotine content cigarette advertising: How false beliefs and subjective ratings affect smoking behavior.

INTRODUCTION: Tobacco advertising can create false beliefs about health harms that are reinforced by product design features. Reduced nicotine content (RNC) cigarettes may reduce harm, but research has not addressed advertising influences. This study examined RNC cigarette advertising effects on false harm beliefs, and how these beliefs - along with initial subjective ratings of RNC cigarettes - affect subsequent smoking behaviors. We further explored whether subjective ratings moderate associations between false beliefs and behavior. METHODS: Seventy-seven daily, non-treatment-seeking smokers (66.2% male) participated in the first 15days of a randomized, controlled, open-label RNC cigarette trial. Participants viewed an RNC cigarette advertisement at baseline before completing a 5-day period of preferred brand cigarette use, followed by a 10-day period of RNC cigarette use (0.6mg nicotine yield). Participants provided pre- and post-advertisement beliefs, and subjective ratings and smoking behaviors for cigarettes smoked during laboratory visits. RESULTS: Viewing the advertisement increased beliefs that RNC cigarettes contain less nicotine and are healthier than regular cigarettes (p's<0.001 and 0.011), and decreased the belief that they are less likely to cause cancer (p=0.046). Neither false beliefs nor subjective ratings directly affected smoking behaviors. Significant interactions of strength and taste ratings with beliefs (p's<0.001), however, indicated that among smokers with less negative initial subjective ratings, greater false beliefs were associated with greater RNC cigarette consumption. CONCLUSIONS: Smokers may misconstrue RNC cigarettes as less harmful than regular cigarettes. These beliefs, in conjunction with favorable subjective ratings, may increase product use.

Bladder-cancer-associated mutations in RXRA activate peroxisome proliferator-activated receptors to drive urothelial proliferation.

RXRA regulates transcription as part of a heterodimer with 14 other nuclear receptors, including the peroxisome proliferator-activated receptors (PPARs). Analysis from TCGA raised the possibility that hyperactive PPAR signaling, either due to PPAR gamma gene amplification or RXRA hot-spot mutation (S427F/Y) drives 20-25% of human bladder cancers. Here, we characterize mutant RXRA, demonstrating it induces enhancer/promoter activity in the context of RXRA/PPAR heterodimers in human bladder cancer cells. Structure-function studies indicate that the RXRA substitution allosterically regulates the PPAR AF2 domain via an aromatic interaction with the terminal tyrosine found in PPARs. In mouse urothelial organoids, PPAR agonism is sufficient to drive growth-factor-independent growth in the context of concurrent tumor suppressor loss. Similarly, mutant RXRA stimulates growth-factor-independent growth of Trp53/Kdm6a null bladder organoids. Mutant RXRA-driven growth of urothelium is reversible by PPAR inhibition, supporting PPARs as targetable drivers of bladder cancer.

Disrupting Foxh1-Groucho interaction reveals robustness of nodal-based embryonic patterning.

The winged-helix transcription factor Foxh1 is an essential regulator of Nodal signaling during the key developmental processes of gastrulation, anterior-posterior (A-P) patterning, and the derivation of left-right (L-R) asymmetry. Current models have Foxh1 bound to phospho-Smad2/3 (pSmad2/3) as a central transcriptional activator for genes targeted by Nodal signaling including Nodal itself, the feedback inhibitor Lefty2, and the positive transcriptional effector Pitx2. However, the conserved Engrailed homology-1 (EH1) motif present in Foxh1 suggests that modulated interaction with Groucho (Grg) co-repressors would allow Foxh1 to function as a transcriptional switch, toggling between transcriptional on and off states via pSmad2-Grg protein-switching, to ensure the properly timed initiation and suppression, and/or amplitude, of expression of Nodal and its target genes. We minimally mutated the Foxh1 EH1 motif, creating a novel Foxh1(mEH1) allele to test directly the contribution of Foxh1-Grg-mediated repression on the transient, dynamic pattern of Nodal signaling in mice. All aspects of Nodal and its target gene expression in Foxh1(mEH1/mEH1) embryos were equivalent to wild type. A-P patterning and organ situs in homozygous embryos and adult mice were also unaffected. The finding that Foxh1-Grg-mediated repression is not essential for Nodal expression during mouse embryogenesis suggests that other regulators compensate for the loss of repressive regulatory input that is mediated by Grg interactions. We suggest that the pervasive inductive properties of Nodal signaling exist within the context of a strongly buffered regulatory system that contributes to resilience and accuracy of its dynamic expression pattern.