Notch1 binds and induces degradation of Snail in hepatocellular carcinoma

<p>Abstract</p> <p>Background</p> <p>Hepatocellular carcinoma (HCC) is a common, highly invasive malignant tumor associated with a high mortality rate. We previously reported that the aberrant expression of Snail via activation of reactive oxygen species contributes to the invasive property of HCC, in part by downregulation of E-cadherin through both transcriptional repression and epigenetic modification of the E-cadherin promoter. Having demonstrated the ability of Snail to bind and recruit histone deacetylase 1 and DNA methyltransferase 1 in this context, we set out to look for other interactions that could affect its ability to promote oncogenic transformation and cancer cell invasion.</p> <p>Results</p> <p>Using cells that stably expressed Snail, we characterized Snail protein interactors by tandem affinity purification and mass spectrometry. Immunoprecipitation and subcellular colocalization studies were performed to confirm our identification of the Notch1 intracellular domain (NICD) as a novel Snail-binding partner. NICD interaction with Snail was found to induce ubiquitination and MDM2-dependent degradation of Snail. Interestingly, NICD inhibited Snail-dependent invasive properties in both HCC cells and mouse embryonic fibroblasts.</p> <p>Conclusions</p> <p>Our study demonstrates that NICD can oppose Snail-dependent HCC cell invasion by binding and inducing proteolytic degradation of Snail. Although Notch signaling and Snail are both widely considered tumor-promoting factors, our findings indicate that the individual oncogenic contribution of Notch1 and Snail in malignant systems should be interpreted carefully, particularly when they are conjointly expressed.</p

Ring finger protein 126 (RNF126) suppresses ionizing radiation-induced p53-binding protein 1 (53BP1) focus formation

Cells have evolved sophisticated mechanisms to maintain genomic integrity in response to DNA damage. Ionizing radiation (IR)-induced DNA damage results in the formation of IR-induced foci (iRIF) in the nucleus. The iRIF formation is part of the DNA damage response (DDR), which is an essential signaling cascade that must be strictly regulated because either the loss of or an augmented DDR leads to loss of genome integrity. Accordingly, negative regulation of the DDR is as critical as its activation. In this study, we have identified ring finger protein 126 (RNF126) as a negative regulator of the DDR from a screen of iRIF containing 53BP1. RNF126 overexpression abolishes not only the formation of 53BP1 iRIF but also of RNF168, FK2, RAP80, and BRCA1. However, the iRIF formation of H2AX, MDC1, and RNF8 is maintained, indicating that RNF126 acts between RNF8 and RNF168 during the DDR. In addition, RNF126 overexpression consistently results in the loss of RNF168-mediated H2A monoubiquitination at lysine 13/15 and inhibition of the non-homologous end joining capability. Taken together, our findings reveal that RNF126 is a novel factor involved in the negative regulation of DDR, which is important for sustaining genomic integrity

Thrap3 promotes R-loop resolution via interaction with methylated DDX5

Transcription-replication conflicts lead to DNA damage and genomic instability, which are closely related to human diseases. A major source of these conflicts is the formation of R-loops, which consist of an RNA-DNA hybrid and a displaced single-stranded DNA. Although these structures have been studied, many aspects of R-loop biology and R-loop-mediated genome instability remain unclear. Here, we demonstrate that thyroid hormone receptor-associated protein 3 (Thrap3) plays a critical role in regulating R-loop resolution. In cancer cells, Thrap3 interacts with DEAD-box helicase 5 (DDX5) and localizes to R-loops. Arginine-mediated methylation of DDX5 is required for its interaction with Thrap3, and the Thrap3-DDX5 axis induces the recruitment of 5&apos;-3&apos; exoribonuclease 2 (XRN2) into R-loops. Loss of Thrap3 increases R-loop accumulation and DNA damage. These findings suggest that Thrap3 mediates resistance to cell death by preventing R-loop accumulation in cancer cells. Cancer: DNA damage associated with nucleic acid loops A nuclear protein appears to inhibit cancer cell death by preventing the accumulation of nucleic acid structures called R-loops. R-loops are by-products of transcription, comprising two misaligned DNA strands and one RNA strand. They are involved in gene expression, but also threaten genome integrity and have been linked to the onset of neurodegeneration and cancers. A team led by Jang Hyun Choi and Hyug Moo Kwon, Ulsan National Institute of Science and Technology, South Korea, explored the role of Thrap3, a nuclear protein involved in RNA splicing, in R-loop-associated DNA damage. They found that Thrap3 binds to an enzyme essential for resolving R-loops. When the team suppressed Thrap3 expression, they saw an increase in R-loops in both normal and cancer cells. This R-loop accumulation significantly inhibited the growth of breast cancer cells

TonEBP recognizes R-loops and initiates m6A RNA methylation for R-loop resolution

R-loops are three-stranded, RNA???DNA hybrid, nucleic acid structures produced due to inappropriate processing of newly transcribed RNA or transcription-replication collision (TRC). Although R-loops are important for many cellular processes, their accumulation causes genomic instability and malignant diseases, so these structures are tightly regulated. It was recently reported that R-loop accumulation is resolved by methyltransferase-like 3 (METTL3)-mediated m6A RNA methylation under physiological conditions. However, it remains unclear how R-loops in the genome are recognized and induce resolution signals. Here, we demonstrate that tonicity-responsive enhancer binding protein (TonEBP) recognizes R-loops generated by DNA damaging agents such as ultraviolet (UV) or camptothecin (CPT). Single-molecule imaging and biochemical assays reveal that TonEBP preferentially binds a R-loop via both 3D collision and 1D diffusion along DNA in vitro. In addition, we find that TonEBP recruits METTL3 to R-loops through the Rel homology domain (RHD) for m6A RNA methylation. We also show that TonEBP recruits RNaseH1 to R-loops through a METTL3 interaction. Consistent with this, TonEBP or METTL3 depletion increases R-loops and reduces cell survival in the presence of UV or CPT. Collectively, our results reveal an R-loop resolution pathway by TonEBP and m6A RNA methylation by METTL3 and provide new insights into R-loop resolution processes

Hypomorphic Mutations in TONSL Cause SPONASTRIME Dysplasia

SPONASTRIME dysplasia is a rare, recessive skeletal dysplasia characterized by short stature, facial dysmorphism, and aberrant radiographic findings of the spine and long bone metaphysis. No causative genetic alterations for SPONASTRIME dysplasia have yet been determined. Using whole-exome sequencing (WES), we identified bi-allelic TONSL mutations in 10 of 13 individuals with SPONASTRIME dysplasia. TONSL is a multi-domain scaffold protein that interacts with DNA replication and repair factors and which plays critical roles in resistance to replication stress and the maintenance of genome integrity. We show here that cellular defects in dermal fibroblasts from affected individuals are complemented by the expression of wild-type TONSL. In addition, in vitro cell-based as-says and in silico analyses of TONSL structure support the pathogenicity of those TONSL variants. Intriguingly, a knock-in (KI) Tonsl mouse model leads to embryonic lethality, implying the physiological importance of TONSL. Overall, these findings indicate that genetic variants resulting in reduced function of TONSL cause SPONASTRIME dysplasia and highlight the importance of TONSL in embryonic development and postnatal growth.Peer reviewe

New players in the BRCA1-mediated DNA damage responsive pathway

DNA damage checkpoint is an important self-defense mechanism for the maintenance of genome stability. Defects in DNA damage signaling and repair lead to various disorders and increase tumor incidence in humans. In the past 10 years, we have identified many components involved in the DNA damage-signaling pathway, including the product of breast cancer susceptibility gene 1 (BRCA1). Mutations in BRCA1 are associated with increased risk of breast and ovarian cancers, highlighting the importance of this DNA damage-signaling pathway in tumor suppression. While it becomes clear that BRCA1 plays a crucial role in the DNA damage responsive pathway, exactly how BRCA1 receives DNA damage signals and exerts its checkpoint function has not been fully addressed. A series of recent studies reported the discovery of many novel components involved in DNA damage-signaling pathway. These newly identified checkpoint proteins, including RNF8, RAP80 and CCDC98, work in concern in recruiting BRCA1 to DNA damage sites and thus regulate BRCA1 function in G2/M checkpoint control. This review will summarize these recent findings and provide an updated view of the regulation of BRCA1 in response to DNA damage

The effect of oral bacterial infection on DNA damage response in host cells

Maintaining and transferring intact genomes from one generation to another plays a pivotal role in all living organisms. DNA damage caused by numerous endogenous and exogenous factors must be adequately repaired, as unrepaired and accumulated DNA mutations can cause severe deleterious effects, such as cell death and cancer. To prevent adverse consequences, cells have established DNA damage response mechanisms that address different forms of DNA damage, including DNA double-strand breaks, mismatches, nucleotide excision, and base excision. Among several sources of exogenous DNA damage, bacterial infections cause inflammation in the host, generating reactive oxygen species (ROS) and causing oxidative DNA damage. Recent studies have revealed the importance of the oral microbiome in inflammation and several systemic host diseases. Dysbiosis of oral bacteria can induce chronic inflammation, which enhances ROS-induced DNA damage, and improperly repaired damage can lead to carcinogenesis. This review describes the various DNA repair pathways that are affected by chronic inflammation and the discovery of the DNA damage response induced by oral bacteria such as Porphyromonas gingivalis and Fusobacterium nucleatum.11Nsci

Cobll1: A new player in CML

(c) Kim et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License 3.0 (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.101sci

Watershed environmental impact assessment for extreme climates based on shared socioeconomic pathway climate change scenarios

Abnormal climate phenomena that exceed conventional weather observations occur worldwide, such as severe floods, droughts, and environmental issues, and have attracted increasing attention. To avoid indiscriminate industrialization and achieve sustainable development, environmental experts have presented various opinions based on climate change scenario data. In this study, shared socioeconomic pathway (SSP) climate change scenarios that consider socioeconomic conditions were used to assess the environmental impact of extreme climate conditions on watersheds. Using the UK Earth System Modelling (UKESM1) SSP scenarios, we analyzed the following: 1) Heat index for each SSP climate change scenario using the H-Index; 2) extreme climate for each SSP climate change scenario using the standardized precipitation index (SPI); 3) the impact of extreme climate on non-point pollution using event mean concentration (EMC); and 4) the environmental flow caused by extreme climate by combining the K-water Distributed RUnoff Model (K-DRUM) and global environmental flow calculator (GEFC) models. According to the heat index analysis regarding SSPs climate change scenarios, the heatwave index will continue to rise if high carbon emissions persist. Temperature serves as an important indicator that has the most meaningful impact on ecosystems. The SPI analysis showed an increase in “extremely dry” conditions, and overall, more severe droughts are likely to occur due to high carbon emission-induced climate change. The nonpoint source pollution is also higher in climate change scenarios with high carbon emissions. The extreme drought event assessment using SPI and environmental flow revealed a shift from the “moist conditions” category to grade C. Our assessments in this study conclusively indicate that drought frequency will increase along with nonpoint source pollution. Furthermore, environmental flows will shift to grade C, resulting in the disappearance of some sensitive ecological species and an increase in invasive species. These analyses determined that high carbon emission-induced climate change caused leads to severe droughts and significant alterations in the overall water circulation, thereby complicating water resource management. Furthermore, we identified watersheds that are highly vulnerable to climate change and designated these as “mid-watersheds” that first require non-point pollution management. Here, the aquatic ecosystem environment can be affected by climate change without any artificial environmental influence. Various research-based analysis methods based on modeling have been presented using SSP climate change scenarios, and are highly beneficial for establishing policies and coping strategies for environmental preservation and sustainable development

Ubiquitin-binding protein RAP80 mediates BRCA1-dependent DNA damage response

Mutations in the breast cancer susceptibility gene 1 (BRCA1) are associated with an increased risk of breast and ovarian cancers. BRCA1 participates in the cellular DNA damage response. We report the identification of receptor-associated protein 80 (RAP80) as a BRCA1-interacting protein in humans. RAP80 contains a tandem ubiquitin-interacting motif domain, which is required for its binding with ubiquitin in vitro and its damage-induced foci formation in vivo. Moreover, RAP80 specifically recruits BRCA1 to DNA damage sites and functions with BRCA1 in G(2)/M checkpoint control. Together, these results suggest the existence of a ubiquitination-dependent signaling pathway involved in the DNA damage response