JAC1 Targets YY1-Mediated JWA/p38 MAPK Signaling to Inhibit Proliferation and Induce Apoptosis in TNBC

Background:Triple negative breast cancer (TNBC)is a type of breast cancer with poor prognosis, and still has no adequate therapeutic target and ideal medicine.The public database and the relative studies have shown that low expression of JWA is closely related to the poor overall survival in many cancers including breast cancer. However, the precise biological functions and behind mechanisms of JWA in TNBC are still unclear.Methods:Both TCGA and GEO databases were used to confirm the relationship between expression levels of JWA and overall survival inTNBC cases.JAC1, an agonisticsmall compound of JWA gene, was used in TNBC modelsin vitro and in vivo. The routine cellular and molecular assays include CCK-8, colony formation, EdUincorporation, the flow cytometry, Western blot, immunohistochemistry,immune-fluorescence microscopy and reporter gene assays were conducted in this study.Results:Low expression of JWA was associated with poor prognosis in TNBC patients. JAC1 treatment inhibited TNBCcells proliferation and promoted apoptosis in vitro and in vivo. JAC1 specifically combined and targeted YY1toeliminate its transcriptional inhibition on JWA gene.At the same time, JAC1promoted ubiquitination and degradation of YY1. The rescued JWA induced G1 phase arrest and apoptosis in TNBC cellsthrough the p38 MAPK signaling pathway. In addition, JAC1 disrupted the interaction between YY1 and HSF1, and suppressed the oncogenic role of HSF1 in TNBC throughp-Aktsignaling pathway.Conclusions:We discovered for the first time that JAC1 is a YY1 targeting compoundand maybe a potential therapeutic agent for TNBC.

Respiratory Syncytial Virus Matrix Protein-Chromatin Association Is Key to Transcriptional Inhibition in Infected Cells

The morbidity and mortality caused by the globally prevalent human respiratory pathogen respiratory syncytial virus (RSV) approaches that world-wide of influenza. We previously demonstrated that the RSV matrix (M) protein shuttles, in signal-dependent fashion, between host cell nucleus and cytoplasm, and that this trafficking is central to RSV replication and assembly. Here we analyze in detail the nuclear role of M for the first time using a range of novel approaches, including quantitative analysis of de novo cell transcription in situ in the presence or absence of RSV infection or M ectopic expression, as well as in situ DNA binding. We show that M, dependent on amino acids 110–183, inhibits host cell transcription in RSV-infected cells as well as cells transfected to express M, with a clear correlation between nuclear levels of M and the degree of transcriptional inhibition. Analysis of bacterially expressed M protein and derivatives thereof mutated in key residues within M’s RNA binding domain indicates that M can bind to DNA as well as RNA in a cell-free system. Parallel results for point-mutated M derivatives implicate arginine 170 and lysine 172, in contrast to other basic residues such as lysine 121 and 130, as critically important residues for inhibition of transcription and DNA binding both in situ and in vitro. Importantly, recombinant RSV carrying arginine 170/lysine 172 mutations shows attenuated infectivity in cultured cells and in an animal model, concomitant with altered inflammatory responses. These findings define an RSV M-chromatin interface critical for host transcriptional inhibition in infection, with important implications for anti-RSV therapeutic development.

Targeting cancer cell plasticity by HDAC inhibition to reverse EBV-induced dedifferentiation in nasopharyngeal carcinoma

Application of differentiation therapy targeting cellular plasticity for the treatment of solid malignancies has been lagging. Nasopharyngeal carcinoma (NPC) is a distinctive cancer with poor differentiation and high prevalence of Epstein-Barr virus (EBV) infection. Here, we show that the expression of EBV latent protein LMP1 induces dedifferentiated and stem-like status with high plasticity through the transcriptional inhibition of CEBPA. Mechanistically, LMP1 upregulates STAT5A and recruits HDAC1/2 to the CEBPA locus to reduce its histone acetylation. HDAC inhibition restored CEBPA expression, reversing cellular dedifferentiation and stem-like status in mouse xenograft models. These findings provide a novel mechanistic epigenetic-based insight into virus-induced cellular plasticity and propose a promising concept of differentiation therapy in solid tumor by using HDAC inhibitors to target cellular plasticity.

The novel role of circular RNA ST3GAL6 on blocking gastric cancer malignant behaviors through autophagy regulated by the FOXP2/MET/mTOR axis

Gastric cancer (GC) ranks third in motality among all cancers worldwide. Circular RNAs (circRNAs) play essential roles in the malignant progression and metastasis of gastric cancer. As a transcription factor, FOXP2 is involved in the progression of many tumours. However, the regulation and association between circRNAs and FOXP2 remain to be discovered. In our study, CircST3GAL6 was significantly depressed in GC tissues and cells. circST3GAL6 overexpression inhibited the proliferation, invasion and metastasis of GC cells in vitro and in vivo. Importantly, circST3GAL6 overexpression induced apoptosis and promote autophagy in GC cells. Furthermore, we found that circST3GAL6 sponged miR-300 and subsequently regulated FOXP2. We further revealed that FOXP2 suppressed the activation of the Met/AKT/mTOR axis, a classic pathway that regulates autophagy-mediated proliferation and migration. In summary, our findings revealed that circST3GAL6 functions as a tumour suppressor through the miR-300/FOXP2 axis in GC, regulates apoptosis and autophagy through FOXP2-mediated transcriptional inhibition of the MET axis and may be a biomarker for GC treatment.

RNase HI depletion strongly potentiates cell killing by rifampicin in mycobacteria

Multidrug resistant (MDR) tuberculosis (TB) is defined by the resistance of Mycobacterium tuberculosis, the causative organism, to the first-line antibiotics rifampicin and isoniazid. Mitigating or reversing resistance to these drugs offers a means of preserving and extending their use in TB treatment. R-loops are RNA/DNA hybrids that are formed in the genome during transcription, and can be lethal to the cell if not resolved. RNase HI is an enzyme that removes R-loops, and this activity is essential in M. tuberculosis: knockouts of rnhC, the gene encoding RNase HI, are non-viable. This essentiality supports it as a candidate target for the development of new antibiotics. In the model organism Mycolicibacterium smegmatis, RNase HI activity is provided by two RNase HI enzymes, RnhA and RnhC. We show that the partial depletion of RNase HI activity in M. smegmatis, by knocking out either of the genes encoding RnhA or RnhC, led to the accumulation of R-loops. The sensitivity of the knockout strains to the antibiotics moxifloxacin, streptomycin and rifampicin was increased, with sensitivity to the transcriptional inhibitor rifampicin strikingly increased by nearly 100-fold. We also show that R-loop accumulation accompanies partial transcriptional inhibition, suggesting a mechanistic basis for the synergy between RNase HI depletion and transcriptional inhibition. A model of how transcriptional inhibition can potentiate R-loop accumulation is presented. Finally, we identified four small molecules that inhibit recombinant RnhC activity and that also potentiated rifampicin activity in whole-cell assays against M. tuberculosis, supporting an on-target mode of action, and providing the first step in developing a new class of anti-mycobacterial drug.

m(6)A mRNA Methylation Regulates Ferroptosis in HPSCC by Targeting NFE2L2/NRF2

Background Emerging as the most abundant posttranscriptional internal mRNA modification in eukaryotes, N6-methyladenosine (m6A) modification has gathered tremendous scientific interest in recent years. However, no study addresses the role of m6A modification in ferroptosis. Here, we showed that m6A modifications are decreased in RSL3-induced ferroptosis in hypopharyngeal squamous cell carcinoma (HPSCC). We found that AlkB homolog 5 (ALKBH5), one of the m6A demethylases, is the primary factor involved in aberrant m6A modification. Methods Bioinformatics analysis, sample analysis, cell biological analyses and transcriptome sequencing were performed to evaluate the correlation between m6A modification and ferroptosis as well as molecular mechanism of ALKBH5 function. Transcriptome-wide m6A-seq and RIP-seq data and following m6A dot blot, MeRIP-qPCR, RIP-qPCR and dual luciferase reporter assays were mapped to screen and validate the candidate targets of ALKBH5. Results ALKBH5-knockdown impaired ferroptotic cell death in HPSCC. However, overexpression of ALKBH5 has an opposite effect, suggesting that ALKBH5 is a positive regulator of ferroptosis. Mechanistically, ALKBH5-mediated m6A demethylation led to a post-transcriptional inhibition of NFE2L2/NRF2, the central player in the regulation of antioxidant molecules in cells, at two m6A residues in the 3ʹ-UTR. Therefore, knocking down ALKBH5 subsequently increases the expression levels of NFE2L2/NRF2 and increased cell resistance to ferroptosis. In addition, m6A-mediated NFE2L2/NRF2 stabilization relied on the m6A reader IGF2BP2. Conclusion ALKBH5 functions as a tumor suppresser through ferroptosis in HPSCC. ALKBH5 destabilizes NFE2L2/NRF2 expression in HPSCC through an m6A-IGF2BP2-dependent mechanism. Together, our work uncovers a critical link between ALKBH5-NFE2L2/NRF2 and ferroptosis, providing insight into the functional importance of the reversible mRNA m6A methylation and its modulators in HPSCC.

OsSPL14/17 are required for phosphate-deficiency-inhibited tiller bud outgrowth by repression of PIN2 in rice

Phosphorus (P) is an essential nutrient for food crops. P-deficiency inhibits tiller development of rice; thus, an understanding of the P-modulated tiller development mechanism is crucial for grain yield. Auxin and strigolactones (SLs) have been implicated as regulators of tiller formation in rice. However, the relationships between the two are unclear. We found that low-P (LP) inhibited rice tiller formation and tiller bud elongation, with higher levels of SLs. In contrast to wild-type (WT) plants, the number of tillers was greater in d10 (SL biosynthesis mutant), d14, and d53 (SL-responsive mutants) under LP conditions, demonstrating that D53 participates in LP- mediated inhibition of rice tiller formation. The strong interaction between D53 and SPL14/17 inhibited their transcriptional activities under normal P (NP) conditions, and mutation of SPL14/17 eliminated their inhibitory effects on tiller formation under LP conditions. SPL14/17 inhibited transcriptional from the PIN2 promoter, and overexpression of PIN2 induced tiller development under LP conditions. Therefore, binding of D53 to SPL14/17 represses their transcriptional inhibition, reversing SPL14/17-inhibited PIN2 transcription and promoting tiller development under NP conditions. Proteasomal degradation of D53 releases SPL14/17, thus repressing PIN2 transcription and preventing induction of tillering under LP conditions.