SUMOylation of the ubiquitin ligase component KEAP1 at K39 upregulates NRF2 and its target function in lung cancer cell proliferation.

Nuclear Factor Erythroid 2-Related Factor 2 (NRF2) is important for the expression of genes associated with oxidative stress. The levels of NRF2 are controlled by Kelch-like ECH-associated protein 1 (KEAP1)-dependent degradation. Although oxidative stress is known to suppress KEAP1 activity to stabilize the levels of NRF2, the mechanism for this control is unclear. Here, we identify that KEAP1 is modified by SUMO1 at the lysine residue position 39 (K39). Arginine replacement of this lysine (K39R) in KEAP1 did not affect its stability, subcellular localization, or dimerization but promoted the formation of the Cullin 3 ubiquitin ligase and increased NRF2 ubiquitination. This was accompanied by decreased NRF2 expression. Gene reporter assays showed that the transcription of antioxidant response elements was heightened in KEAP1-WT cells compared to cells expressing the KEAP1-K39R SUMO1 substrate mutant. Consistent with this, chromatin immunoprecipitation assays revealed higher NRF2 binding to the promoter regions of antioxidant genes in cells expressing the KEAP1-WT compared to the KEAP1-K39R mutant protein in H1299 lung cancer cell. The significance of this suppression of KEAP1 activity by its SUMOylation was tested in a subcutaneous tumor model of H1299 lung cancer cell lines that differentially expressed the WT and K39R KEAP1 constructs. This model showed that mutating the SUMOylation site on KEAP1 altered the production of reactive oxygen species and suppressed tumor growth. Taken together, our study recognizes that NRF2-dependent redox control is regulated by the SUMOylation of KEAP1. These findings identify a potential new therapeutic option to counteract oxidative stress.

HDAC6 inhibitor promotes reactive oxygen species-meditated clearance of Staphylococcus aureus in macrophage.

Staphylococcus aureus (S. aureus) pneumonia has become an increasingly important public health problem. Recent evidence suggests that epigenetic modifications are critical in the host immune defence against pathogen infection. In this study, we found that S. aureus infection induces the expression of histone deacetylase 6 (HDAC6) in a dose-dependent manner. Furthermore, by using a S. aureus pneumonia mouse model, we showed that the HDAC6 inhibitor, tubastatin A, demonstrates a protective effect in S. aureus pneumonia, decreasing the mortality and destruction of lung architecture, reducing the bacterial burden in the lungs and inhibiting inflammatory responses. Mechanistic studies in primary bone marrow-derived macrophages demonstrated that the HDAC6 inhibitors, tubastatin A and tubacin, reduced the intracellular bacterial load by promoting bacterial clearance rather than regulating phagocytosis. Finally, N-acetyl-L- cysteine, a widely used reactive oxygen species (ROS) scavenger, antagonized ROS production and significantly inhibited tubastatin A-induced S. aureus clearance. These findings demonstrate that HDAC6 inhibitors promote the bactericidal activity of macrophages by inducing ROS, an important host factor for S. aureus clearance and production. Our study identified HDAC6 as a suitable epigenetic modification target for preventing S. aureus infection, and tubastatin A as a useful compound in treating S. aureus pneumonia.

Identification and Characterization of Extrachromosomal Circular DNA in Plasma of Lung Adenocarcinoma Patients.

Background: Chromosome is the basic framework for eukaryotic cells to store genetic information, but certain genes exist in circulation, such as extrachromosomal circular DNA (eccDNA). The unique genetic characteristics and structure of eccDNA provide a new vision on the early diagnosis of cancer; however, whether eccDNA contributes to the early diagnosis and progression of lung cancer remains unclear. Methods: We performed next-generation sequencing (NGS) analysis of eccDNA from the plasma of 6 lung adenocarcinoma (LUAD) patients. The data of plasma eccDNA of healthy people were obtained from public available database. We compared size distribution, chromosome origin, formation and expression patterns of eccDNA between LUAD patients and those of 6 healthy people and 4 healthy gravidas. Results: A total number of 716,059 eccDNA ranging from 22 bp to 3,297,519 bp were detected with an average size less than 800bp and distinctive bimodality in size around 191 bp and 320 bp. After comparison of eccDNA abundance in each sequencing sample, nine eccDNA were ranked on top with higher frequency in lung adenocarcinoma patients than healthy people. Among them, four eccDNA (DOCK1, PPIC, TBC1D16, and RP11-370A5.1) were uniquely expressed in lung adenocarcinoma patients, which may serve as potential biomarkers for early diagnosis LUAD. Conclusion: Cancer-specific eccDNA was presented in LUAD compared to normal people, which might serve as a promising biomarker in LUAD.