Alexander Vu

Regulatory T (T _reg ) cells in mice can lose lineage identity and acquire proinflammatory functions, but whether human T _reg cells are similarly susceptible to cytokine-driven destabilization remains unclear. Here we established an in vitro model of human T _reg cell destabilization defined by silencing of the lineage-specifying transcription factor FOXP3, loss of suppressive function and acquisition of proinflammatory activity. Single-cell chromatin accessibility and transcriptomic profiling revealed a genome-wide increase in accessibility at AP-1-binding sites, including a putative regulatory element distal to IRF4 . Increased accessibility at this element correlated with increased IRF4 expression during T _reg cell destabilization, and its excision conferred resistance to inflammatory cytokine-induced reprogramming. Conversely, forced expression of IRF4 together with BATF promoted T _reg cell destabilization. These data identify a distal IRF4 regulatory element as a critical node enabling heightened AP-1-IRF4 cooperative activity to drive T _reg cell destabilization, with implications for the design of more stable and effective T _reg cell-based therapies.

The venerable 1,3-dipolar cycloaddition has been widely used in organic synthesis for the construction of various heterocycles. However, in its century-long history, the simple and omnipresent aromatic phenyl ring has remained a stubbornly unreactive dipolarophile. Here we report 1,3-dipolar cycloaddition between aromatic groups and diazoalkenes, generated in situ from lithium acetylides and N-sulfonyl azides. The reaction results in densely functionalized annulated cyclic sulfonamide-indazoles that can be further converted into stable organic molecules that are important in organic synthesis. The involvement of aromatic groups in the 1,3-dipolar cycloadditions broadens the synthetic utility of diazoalkenes, a family of dipoles that have been little explored so far and are otherwise difficult to access. The process described here provides a route for the synthesis of medicinally relevant heterocycles and can be extended to other arene-containing starting materials. Computational examination of the proposed reaction pathway revealed a series of finely orchestrated bond-breaking and bond-forming events that ultimately lead to the annulated products.

Hepatocellular carcinoma (HCC) remains a global health challenge whose incidence is growing worldwide. Previous evidence strongly supported the notion that the circadian clock controls physiological homeostasis of the liver and plays a key role in hepatocarcinogenesis. Despite the progress, cellular and molecular mechanisms underpinning this HCC-clock crosstalk remain unknown. Addressing this knowledge gap, we show here that although the human HCC cells Hep3B, HepG2, and Huh7 displayed variations in circadian rhythm profiles, all cells relied on the master circadian clock transcription factors, BMAL1 and CLOCK, for sustained cell growth. Down-regulating Bmal1 or Clock in the HCC cells induced apoptosis and arrested cell cycle at the G ₂ /M phase. Mechanistically, we found that inhibiting Bmal1 / Clock induced dysregulation of the cell cycle regulators Wee1 and p21 which cooperatively contribute to tumor cell death. Bmal1 / Clock knockdown caused downregulation of Wee1 that led to apoptosis activation and upregulation of p21 which arrested the cell cycle at the G ₂ /M phase. Collectively, our results suggest that the circadian clock regulators BMAL1 and CLOCK promote HCC cell proliferation by controlling Wee1 and p21 levels, thereby preventing apoptosis and cell cycle arrest. Our findings shed light on cellular impact of the clock proteins for maintaining HCC oncogenesis and provide proof-of-principle for developing cancer therapy based on modulation of the circadian clock.