No abstract

Double-strand breaks repaired by homologous recombination (HR) are first resected to form single-stranded DNA, which binds replication protein A (RPA). RPA attracts mediators that load the Rad51 filament to promote strand invasion, the defining feature of HR. How the resection machinery navigates nucleosome-packaged DNA is poorly understood. Here we report that in Schizosaccharomyces pombe a conserved DDB1-CUL4-associated factor (DCAF), Wdr70, is recruited to DSBs as part of the Cullin4-DDB1 ubiquitin ligase (CRL4Wdr70) and stimulates distal H2B lysine 119 mono-ubiquitination (uH2B). Wdr70 deletion, or uH2B loss, results in increased loading of the checkpoint adaptor and resection inhibitor Crb253BP1, decreased Exo1 association and delayed resection. Wdr70 is dispensable for resection upon Crb253BP1 loss, or when the Set9 methyltransferase that creates docking sites for Crb2 is deleted. Finally, we establish that this histone regulatory cascade similarly controls DSB resection in human cells.

No abstract

As an effective antimalarial drug, Dihydroartemisinin (DHA) is readily isolated from the traditional Chinese medicine of Artemisia annua. DHA is not only an autophagy promoter but also a substance with strong antitumor efficiency. The relationship between autophagy and inflammasomes has been suggested in hepatocellular carcinoma (HCC). However, there are few reports describing relationships between inflammasomes and autophagy in HCC therapy. The present study demonstrated that DHA suppressed cell proliferation in HepG2215 cells in a dose‐ and time‐dependent manner. The inhibitory activity is mediated by autophagy, in which reactive oxygen species (ROS) production induced nuclear and mitochondrial DNA damage. Then, DHA were first shown to promote AIM2/caspase‐1 inflammasome. Compared with the DHA group, the autophagy inhibitor 3‐MA significantly inhibited the expressions of activated Caspase‐1, a pyroptotic marker proteins. Meanwhile, repression of mTOR by rapamycin promoted autophagy and AIM2/caspase‐1 activation. The caspase‐1 inhibitor Z‐YVAD‐FMK also notably blocked autophagy cell death characterized by the downexpression of Beclin‐1 and LC3‐II. Additionally, the study demonstrated that DHA suppressed pseudopodium formation and cell mobility. Therefore, we first reveal a novel mechanism that DHA promotes AIM2/caspase‐1 inflammasome, which contributes to autophagy in HepG2215 cells. Moreover, nuclear and mitochondrial DNA damage was also involved in this process via ROS production.