KDM6A-SND1 interaction maintains genomic stability by protecting the nascent DNA and contributes to cancer chemoresistance.

Genomic instability is one of the hallmarks of cancer. While loss of histone demethylase KDM6A increases the risk of tumorigenesis, its specific role in maintaining genomic stability remains poorly understood. Here, we propose a mechanism in which KDM6A maintains genomic stability independently on its demethylase activity. This occurs through its interaction with SND1, resulting in the establishment of a protective chromatin state that prevents replication fork collapse by recruiting of RPA and Ku70 to nascent DNA strand. Notably, KDM6A-SND1 interaction is up-regulated by KDM6A SUMOylation, while KDM6AK90A mutation almost abolish the interaction. Loss of KDM6A or SND1 leads to increased enrichment of H3K9ac and H4K8ac but attenuates the enrichment of Ku70 and H3K4me3 at nascent DNA strand. This subsequently results in enhanced cellular sensitivity to genotoxins and genomic instability. Consistent with these findings, knockdown of KDM6A and SND1 in esophageal squamous cell carcinoma (ESCC) cells increases genotoxin sensitivity. Intriguingly, KDM6A H101D & P110S, N1156T and D1216N mutations identified in ESCC patients promote genotoxin resistance via increased SND1 association. Our finding provides novel insights into the pivotal role of KDM6A-SND1 in genomic stability and chemoresistance, implying that targeting KDM6A and/or its interaction with SND1 may be a promising strategy to overcome the chemoresistance.

Hepatitis B virus infection disrupts homologous recombination in hepatocellular carcinoma by stabilizing resection inhibitor ADRM1.

Many cancers harbor homologous recombination defects (HRDs). A HRD is a therapeutic target that is being successfully utilized in treatment of breast/ovarian cancer via synthetic lethality. However, canonical HRD caused by BRCAness mutations do not prevail in liver cancer. Here we report a subtype of HRD caused by the perturbation of a proteasome variant (CDW19S) in hepatitis B virus-bearing (HBV-bearing) cells. This amalgamate protein complex contained the 19S proteasome decorated with CRL4WDR70 ubiquitin ligase, and assembled at broken chromatin in a PSMD4Rpn10- and ATM-MDC1-RNF8-dependent manner. CDW19S promoted DNA end processing via segregated modules that promote nuclease activities of MRE11 and EXO1. Contrarily, a proteasomal component, ADRM1Rpn13, inhibited resection and was removed by CRL4WDR70-catalyzed ubiquitination upon commitment of extensive resection. HBx interfered with ADRM1Rpn13 degradation, leading to the imposition of ADRM1Rpn13-dependent resection barrier and consequent viral HRD subtype distinguishable from that caused by BRCA1 defect. Finally, we demonstrated that viral HRD in HBV-associated hepatocellular carcinoma can be exploited to restrict tumor progression. Our work clarifies the underlying mechanism of a virus-induced HRD subtype.

Requirement of WDR70 for POLE3-mediated DNA double-strand breaks repair.

H2BK120ub1 triggers several prominent downstream histone modification pathways and changes in chromatin structure, therefore involving it into multiple critical cellular processes including DNA transcription and DNA damage repair. Although it has been reported that H2BK120ub1 is mediated by RNF20/40 and CRL4WDR70, less is known about the underlying regulation mechanism for H2BK120ub1 by WDR70. By using a series of biochemical and cell-based studies, we find that WDR70 promotes H2BK120ub1 by interacting with RNF20/40 complex, and deposition of H2BK120ub1 and H3K79me2 in POLE3 loci is highly sensitive to POLE3 transcription. Moreover, we demonstrate that POLE3 interacts CHRAC1 to promote DNA repair by regulation on the expression of homology-directed repair proteins and KU80 recruitment and identify CHRAC1 D121Y mutation in colorectal cancer, which leads to the defect in DNA repair due to attenuated the interaction with POLE3. These findings highlight a previously unknown role for WDR70 in maintenance of genomic stability and imply POLE3 and CHRAC1 as potential therapeutic targets in cancer.

Targeting CRL4 suppresses chemoresistant ovarian cancer growth by inducing mitophagy.

Chemoresistance has long been the bottleneck of ovarian cancer (OC) prognosis. It has been shown that mitochondria play a crucial role in cell response to chemotherapy and that dysregulated mitochondrial dynamics is intricately linked with diseases like OC, but the underlying mechanisms remain equivocal. Here, we demonstrate a new mechanism where CRL4CUL4A/DDB1 manipulates OC cell chemoresistance by regulating mitochondrial dynamics and mitophagy. CRL4CUL4A/DDB1 depletion enhanced mitochondrial fission by upregulating AMPKαThr172 and MFFSer172/Ser146 phosphorylation, which in turn recruited DRP1 to mitochondria. CRL4CUL4A/DDB1 loss stimulated mitophagy through the Parkin-PINK1 pathway to degrade the dysfunctional and fragmented mitochondria. Importantly, CRL4CUL4A/DDB1 loss inhibited OC cell proliferation, whereas inhibiting autophagy partially reversed this disruption. Our findings provide novel insight into the multifaceted function of the CRL4 E3 ubiquitin ligase complex in regulating mitochondrial fission, mitophagy, and OC chemoresistance. Disruption of CRL4CUL4A/DDB1 and mitophagy may be a promising therapeutic strategy to overcome chemoresistance in OC.

Claudin-2 promotes colorectal cancer growth and metastasis by suppressing NDRG1 transcription.

Colorectal cancer (CRC) is one of the most common malignant tumours, with multiple driving factors and biological transitions involved in its development. Claudin-2 (CLDN2), a well-defined component of cellular tight junction, has been indicated to associate with CRC progression. However, the function of CLDN2 and the underlying mechanism whereby the downstream signalling transduction is regulated in CRC remains largely unclear. In this study, we demonstrated that CLDN2 is upregulated in CRC samples and associated with poor survival. And CLDN2 depletion significantly promotes N-myc downstream-regulated gene 1 (NDRG1) transcription, leading to termination of the CRC growth and metastasis in vitro and in vivo. Mechanistically, this process promotes CLDN2/ZO1/ZONAB complex dissociation and ZONAB shuttle into nucleus to enrich in the promoter of NDRG1. Thus, this study reveals a novel CLDN2/ZO1/ZONAB-NDRG1 axis in CRC by regulating the expression of EMT-related genes and CDKIs, suggesting CLDN2 may serve as a promising target for CRC treatment.

Systemic inoculation of Escherichia coli causes emergency myelopoiesis in zebrafish larval caudal hematopoietic tissue.

Emergency granulopoiesis occurs in response to severe microbial infection. However, whether and how other blood components, particularly monocytes/macrophages and their progenitors, including hematopoietic stem/progenitor cells (HSPCs), participate in the process and the underlying molecular mechanisms remain unknown. In this study, we challenged zebrafish larvae via direct injection of Escherichia coli into the bloodstream, which resulted in systemic inoculation with this microbe. The reaction of hematopoietic cells, including HSPCs, in the caudal hematopoietic tissue was carefully analysed. Both macrophages and neutrophils clearly expanded following the challenge. Thus, emergency myelopoiesis, including monopoiesis and granulopoiesis, occurred following systemic bacterial infection. The HSPC reaction was dependent on the bacterial burden, manifesting as a slight increase under low burden, but an obvious reduction following the administration of an excessive volume of bacteria. Pu.1 was important for the effective elimination of the microbes to prevent excessive HSPC apoptosis in response to stress. Moreover, Pu.1 played different roles in steady and emergency monopoiesis. Although Pu.1 was essential for normal macrophage development, it played suppressive roles in emergency monopoiesis. Overall, our study established a systemic bacterial infection model that led to emergency myelopoiesis, thereby improving our understanding of the function of Pu.1 in this scenario.

Single-shot analytical assay based on graphene-oxide-modified surface acoustic wave biosensor for detection of single-nucleotide polymorphisms.

The combination of a surface acoustic wave (SAW) biosensor with graphene oxide (GO) provides a promising perspective for detecting DNA mutation. The GO-modified SAW biosensor was prepared by conjugating GO onto the SAW chip surface via electrostatic interaction. Afterward, the probe was immobilized on the GO surface, and detection of DNA mutation was realized by hybridization. The hybridization with a variety of targets would yield different mass and conformational changes on the chip surface, causing the different SAW signals in real time. A total of 137 clinical samples were detected by a single-shot analytical assay based on GO-modified SAW biosensor and direct sequencing in parallel. The diagnostic performance (both sensitivity and specificity) of the assay was evaluated with the direct sequencing as a reference testing method. The phase-shift value of three genotypes in 137 clinical samples was significantly different (p < 0.001). Furthermore, testing of diagnostic performance yielded diagnostic sensitivity and specificity of 100% and 88.6% for identifying CT and CC genotype, 98.0% and 96.2% for identifying CT and TT genotype, respectively. The single-shot analytical assay based on the GO-modified SAW biosensor could be exploited as a potential useful tool to identify CYP2D6*10 polymorphisms in clinical practice of personalized medicine.