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The activation of yes‐associated protein 1 (YAP1) and transcriptional co‐activator with PDZ‐binding motif (TAZ) has been implicated in both regeneration and tumorigenesis, thus representing a double‐edged sword in tissue homeostasis. However, how the activity of YAP1/TAZ is regulated or what leads to its dysregulation in these processes remains unknown. To explore the upstream stimuli modulating the cellular activity of YAP1/TAZ, we developed a highly sensitive YAP1/TAZ/TEAD‐responsive DNA element (YRE) and incorporated it into a lentivirus‐based reporter cell system to allow for sensitive and specific monitoring of the endogenous activity of YAP1/TAZ in terms of luciferase activity in vitro and Venus fluorescence in vivo. Furthermore, by replacing YRE with TCF‐ and NF‐κB‐binding DNA elements, we demonstrated the applicability of this reporter system to other pathways such as Wnt/β‐catenin/TCF‐ and IL‐1β/NF‐κB‐mediated signaling, respectively. The practicality of this system was evaluated by performing cell‐based reporter screening of a chemical compound library consisting of 364 known inhibitors, using reporter‐introduced cells capable of quantifying YAP1/TAZ‐ and β‐catenin‐mediated transcription activities, which led to the identification of multiple inhibitors, including previously known as well as novel modulators of these signaling pathways. We further confirmed that novel YAP1/TAZ modulators, such as potassium ionophores, Janus kinase inhibitors, platelet‐derived growth factor receptor inhibitors, and genotoxic stress inducers, alter the protein level or phosphorylation of endogenous YAP1/TAZ and the expression of their target genes. Thus, this reporter system provides a powerful tool to monitor endogenous signaling activities of interest (even in living cells) and search for modulators in various cellular contexts. [ABSTRACT FROM AUTHOR]

DNA-damaging agents (DDAs) have long been used in cancer therapy. However, the precise mechanisms by which DDAs induce cell death are not fully understood and drug resistance remains a major clinical challenge. Schlafen 11 (SLFN11) was identified as the gene most strongly correlated with the sensitivity to DDAs based on mRNA expression levels. SLFN11 sensitizes cancer cells to DDAs by cleaving and downregulating tRNA Leu (TAA). Elucidating the detailed mechanism by which SLFN11 induces cell death is expected to provide insights into overcoming drug resistance. Here, we show that, upon administration of DDAs, SLFN11 cleaves tRNA Leu (TAA), leading to ER stress and subsequent cell death regulated by inositol-requiring enzyme 1 alpha (IRE1α). These responses were significantly alleviated by SLFN11 knockout or transfection of tRNA Leu (TAA). Our proteomic analysis suggests that tRNA Leu (TAA) influences proteins essential for maintaining proteostasis, especially those involved in ubiquitin-dependent proteolysis. Additionally, we identified the cleavage sites of tRNA Leu (TAA) generated by SLFN11 in cells, and revealed that tRNA fragments contribute to ER stress and cell death. These findings suggest that SLFN11 plays a crucial role in proteostasis by regulating tRNAs, and thus determines cell fate under DDA treatment. Consequently, targeting SLFN11-mediated tRNA regulation could offer a novel approach to improve cancer therapy., Competing Interests: CONFLICT OF INTEREST None declared.

Aldehyde dehydrogenases (ALDHs) are overexpressed in various types of cancers. One of the ALDH family genes, ALDH1A2, is aberrantly expressed in more than 50% of T-cell acute lymphoblastic leukemia (T-ALL) cases. However, its molecular function and role in T-ALL pathogenesis are largely unknown. ChIP-seq and RNA-seq analyses showed that the oncogenic transcription factor TAL1 and its regulatory partners bind to the intronic regulatory element of the ALDH1A2 gene, directly inducing a T-ALL-specific isoform with enzymatic activity. ALDH1A2 was preferentially expressed in the TAL1-positive T-ALL subgroup. In T-ALL cell lines, depletion of ALDH1A2 inhibited cell viability and induced apoptosis. Interestingly, gene expression and metabolomic profiling revealed that ALDH1A2 supported glycolysis and the TCA cycle, accompanied by NADH production, by affecting multiple metabolic enzymes to promote ATP production. Depletion of ALDH1A2 increased the levels of reactive oxygen species (ROS), while ROS levels were reduced by ALDH1A2 overexpression both in vitro and in vivo. Overexpression of ALDH1A2 accelerated tumor onset and increased tumor penetrance in a zebrafish T-ALL model. Taken together, our results indicate that ALDH1A2 protects against intracellular stress and promotes T-ALL cell metabolism and survival. ALDH1A2 overexpression enables leukemic clones to sustain a hyper-proliferative state driven by oncogenes.