EGC enhances tumor antigen presentation and CD8+ T cell-mediated antitumor immunity via targeting oncoprotein SND1.

The Staphylococcal nuclease and Tudor domain containing 1 (SND1) has been identified as an oncoprotein. Our previous study demonstrated that SND1 impedes the major histocompatibility complex class I (MHC-I) assembly by hijacking the nascent heavy chain of MHC-I to endoplasmic reticulum-associated degradation. Herein, we aimed to identify inhibitors to block SND1-MHC-I binding, to facilitate the MHC-I presentation and tumor immunotherapy. Our findings validated the importance of the K490-containing sites in SND1-MHC-I complex. Through structure-based virtual screening and docking analysis, (-)-Epigallocatechin (EGC) exhibited the highest docking score to prevent the binding of MHC-I to SND1 by altering the spatial conformation of SND1. Additionally, EGC treatment resulted in increased expression levels of membrane-presented MHC-I in tumor cells. The C57BL/6J murine orthotopic melanoma model validated that EGC increases infiltration and activity of CD8+ T cells in both the tumor and spleen. Furthermore, the combination of EGC with programmed death-1 (PD-1) antibody demonstrated a superior antitumor effect. In summary, we identified EGC as a novel inhibitor of SND1-MHC-I interaction, prompting MHC-I presentation to improve CD8+ T cell response within the tumor microenvironment. This discovery presents a promising immunotherapeutic candidate for tumors.

Hypomethylation-associated LINC00987 downregulation induced lung adenocarcinoma progression by inhibiting the phosphorylation-mediated degradation of SND1.

DNA methylation, an epigenetic regulatory mechanism dictating gene transcription, plays a critical role in the occurrence and development of cancer. However, the molecular underpinnings of LINC00987 methylation in the regulation of lung adenocarcinoma (LUAD) remain elusive. This study investigated LINC00987 expression in LUAD patients through analysis of The Cancer Genome Atlas data sets. Quantitative real-time polymerase chain reaction (RT-qPCR) and fluorescence in situ hybridization assays were used to assess LINC00987 expression in LUAD. The bisulfite genomic sequence PCR (BSP) assay was used to determine the methylation levels of the LINC00987 promoter. The interaction between LINC00987 and SND1 was elucidated via immunoprecipitation and RNA pull-down assays. The functional significance of LINC00987 and SND1 in Calu-3 and NCI-H1688 cells was evaluated in vitro through CCK-8, EdU, Transwell, flow cytometry, and vasculogenic mimicry (VM) tube formation assays. LINC00987 expression decreased in LUAD concomitant with hypermethylation of the promoter region, while hypomethylation of the LINC00987 promoter in LUAD tissues correlated with tumor progression. Treatment with 5-Aza-CdR augmented LINC00987 expression and inhibited tumor growth. Mechanistically, LINC00987 overexpression impeded LUAD progression and VM through direct binding with SND1, thereby facilitating its phosphorylation and subsequent degradation. Additionally, overexpression of SND1 counteracted the adverse effects of LINC00987 downregulation on cell proliferation, apoptosis, cell migration, invasion, and VM in LUAD in vitro. In conclusion, this pioneering study focuses on the expression and function of LINC00987 and reveals that hypermethylation of the LINC00987 gene may contribute to LUAD progression. LINC00987 has emerged as a potential tumor suppressor gene in tumorigenesis through its binding with SND1 to facilitate its phosphorylation and subsequent degradation.

Hsa_circ_0001583 fuels bladder cancer metastasis by promoting staphylococcal nuclease and tudor domain containing 1-mediated MicroRNA decay.

Muscle-invasive and metastatic bladder cancer indicates extra worse prognosis. Accumulating evidence roots for the prominent role of circular RNAs(circRNAs) in bladder cancer, while the mechanisms linking circRNAs and bladder cancer metastasis remain limitedly investigated. Here, we identified a significantly upregulated circRNA candidate, hsa_circ_0001583, from online datasets. Validated by qRT-PCR, PCR, sanger sequencing, actinomycin D and RNase R digestion experiments, hsa_circ_0001583 was proved to be a genuine circular RNA with higher expression levels in bladder cancer tissue. Through gain and loss of function experiments, hsa_circ_0001583 exhibited potent migration and invasion powers both in vitro and in vivo. The staphylococcal nuclease and Tudor domain containing 1 (SND1) was identified as an authentic binding partner for hsa_circ_0001583 through RNA pulldown and RIP experiments. Elevated levels of hsa_circ_0001583 could bind more to SND1 and protect the latter from degradation. Rescue experiments demonstrated that such interaction-induced increased in SND1 levels in bladder cancer cells enabled the protein to pump its endonuclease activity, leading to the degradation of tumor-suppressing MicroRNAs (miRNAs) including miR-126-3p, the suppressor of Disintegrin And Metalloproteinase Domain-Containing Protein 9 (ADAM9), ultimately driving cells into a highly migrative and invasive state. In summary, our study is the first to highlight the upregulation of hsa_circ_0001583 in bladder cancer and its role in downregulating miR-126-3p by binding to and stabilizing the SND1 protein, thereby promoting bladder cancer cell migration and invasion. This study adds hsa_circ_0001583 to the pool of bladder cancer metastasis biomarkers and therapeutic targets.

[Identification and Analysis of SND1 as an Oncogene and Prognostic Biomarker 
for Lung Adenocarcinoma].

BACKGROUND: Transcription factor (TF) can bind specific sequences that either promotes or represses the transcription of target genes, and exerts important effects on tumorigenesis, migration, invasion. Staphylococcal nuclease-containing structural domain 1 (SND1), which is a transcriptional co-activator, is considered as a promising target for tumor therapy. However, its role in lung adenocarcinoma (LUAD) remains unclear. This study aims to explore the role of SND1 in LUAD. METHODS: Data from The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), Clinical Proteomic Tumor Analysis Consortium (CPTAC), and Human Protein Atlas (HPA) database was obtained to explore the association between SND1 and the prognosis, as well as the immune cell infiltration, and subcellular localization in LUAD tissues. Furthermore, the functional role of SND1 in LUAD was verified in vitro. EdU assay, CCK-8 assay, flow cytometry, scratch assay, Transwell assay and Western blot were performed. RESULTS: SND1 was found to be upregulated and high expression of SND1 is correlated with poor prognosis of LUAD patients. In addition, SND1 was predominantly present in the cytoplasm of LUAD cells. Enrichment analysis showed that SND1 was closely associated with the cell cycle, as well as DNA replication, and chromosome segregation. Immune infiltration analysis showed that SND1 was closely associated with various immune cell populations, including T cells, B cells, cytotoxic cells and dendritic cells. In vitro studies demonstrated that silencing of SND1 inhibited cell proliferation, invasion and migration of LUAD cells. Besides, cell cycle was blocked at G1 phase by down-regulating SND1. CONCLUSIONS: SND1 might be an important prognostic biomarker of LUAD and may promote LUAD cells proliferation and migration.

Vascular injury activates the ELK1/SND1/SRF pathway to promote vascular smooth muscle cell proliferative phenotype and neointimal hyperplasia.

BACKGROUND: Vascular smooth muscle cell (VSMC) proliferation is the leading cause of vascular stenosis or restenosis. Therefore, investigating the molecular mechanisms and pivotal regulators of the proliferative VSMC phenotype is imperative for precisely preventing neointimal hyperplasia in vascular disease. METHODS: Wire-induced vascular injury and aortic culture models were used to detect the expression of staphylococcal nuclease domain-containing protein 1 (SND1). SMC-specific Snd1 knockout mice were used to assess the potential roles of SND1 after vascular injury. Primary VSMCs were cultured to evaluate SND1 function on VSMC phenotype switching, as well as to investigate the mechanism by which SND1 regulates the VSMC proliferative phenotype. RESULTS: Phenotype-switched proliferative VSMCs exhibited higher SND1 protein expression compared to the differentiated VSMCs. This result was replicated in primary VSMCs treated with platelet-derived growth factor (PDGF). In the injury model, specific knockout of Snd1 in mouse VSMCs reduced neointimal hyperplasia. We then revealed that ETS transcription factor ELK1 (ELK1) exhibited upregulation and activation in proliferative VSMCs, and acted as a novel transcription factor to induce the gene transcriptional activation of Snd1. Subsequently, the upregulated SND1 is associated with serum response factor (SRF) by competing with myocardin (MYOCD). As a co-activator of SRF, SND1 recruited the lysine acetyltransferase 2B (KAT2B) to the promoter regions leading to the histone acetylation, consequently promoted SRF to recognize the specific CArG motif, and enhanced the proliferation- and migration-related gene transcriptional activation. CONCLUSIONS: The present study identifies ELK1/SND1/SRF as a novel pathway in promoting the proliferative VSMC phenotype and neointimal hyperplasia in vascular injury, predisposing the vessels to pathological remodeling. This provides a potential therapeutic target for vascular stenosis.

SNHG1, interacting with SND1, contributes to sorafenib resistance of liver cancer cells by increasing m6A-mediated SLC7A11 expression and promoting aerobic glycolysis.

Aerobic glycolysis plays an important role in multidrug resistance of cancer cells. Here, we screened different expressed lncRNAs associated with sorafenib resistance of liver cancer cells, by intersecting the bioinformatics analyses of TCGA and GEO (the GSE62813 dataset) databases. Our results revealed that the 18 upregulated lncRNAs in the intersection are associated with and enriched in metabolism of small molecule organic acids, suggesting their potential in glycolysis. The lncRNA small nucleolar RNA host gene 1 (Snhg1) was chosen as a potential regulator of aerobic glycolysis in liver cancer cells, for its significant promotion on lactate production. Gain- and loss-of-function experiments mediated by Crispr-Cas9 technique in HepG2 cells indicated that Snhg1 promoted cell proliferation, invasion, sorafenib resistance, and aerobic glycolysis. In the mechanism exploration, we found that Snhg1 can interact with SND1 protein, a famous RNA binding protein and recently identified "Reader" of N6-methyladenosine (m6A). SND1 was demonstrated to be positively regulated by Snhg1 and had similar promoting effects on proliferation, invasion, sorafenib resistance, and aerobic glycolysis of HepG2 cells. SND1 bound with and promoted the expression of SLC7A11, an aerobic glycolysis regulator. Furthermore, either silencing SLC7A11 or blocking aerobic glycolysis with 2-deoxy-d-glucose (2-DG) was able to reverse the promotion of Snhg1 overexpression on malignancy, sorafenib resistance, and aerobic glycolysis of HepG2 cells. Finally, in a liver cancer xenograft mouse model, we found that formed tumors with Snhg1-knocked-down HepG2 cells were more sensitive to sorafenib administration. Altogether, SNHG1 contributes to sorafenib resistance of liver cancer cells by promoting SND1-m6A-SLC7A11-mediated aerobic glycolysis.

LncRNA LNC-565686 Promotes Proliferation of Prostate Cancer by Inhibiting Apoptosis through Stabilizing SND1.

Long non-coding RNAs (lncRNAs), typically more than 200 nt long, cannot encode proteins, but can regulate gene expression. They play an indispensable role in the occurrence and progression of various cancers. The main purpose of this study is to discuss the role and mechanism of LNC-565686 in prostate cancer. First, we found an increased expression of LNC-565686 in prostate cancer cells using RNA sequencing, which was further verified using qRT-PCR. Then, catRAPID was used to find that LNC-565686 might regulate SND1. Furthermore, a protein half-life experiment was performed to verify that LNC-565686 could stabilize the expression of SND1. In order to further explore the effects of LNC-565686 and SND1 on prostate cancer cells, we knocked down LNC-565686 and SND1 in prostate cancer cells, and verified using CCK8 and flow cytometry and western blot for the detection of apoptosis-related indicators. Collectively, we have found that LNC-565686 can promote the proliferation of prostate cancer cells and inhibit apoptosis by stabilizing the expression of SND1. Therefore, targeting LNC-565686 might be a new treatment for prostate cancer.

Dynamic regulation of pancreatic ß cell function and gene expression by the SND1 coregulator in vitro.

The pancreatic ß cell synthesizes, packages, and secretes insulin in response to glucose-stimulation to maintain blood glucose homeostasis. Under diabetic conditions, a subset of ß cells fail and lose expression of key transcription factors (TFs) required for insulin secretion. Among these TFs is Pancreatic and duodenal homeobox 1 (PDX1), which recruits a unique subset of transcriptional coregulators to modulate its activity. Here we describe a novel interacting partner of PDX1, the Staphylococcal Nuclease and Tudor domain-containing protein (SND1), which has been shown to facilitate protein-protein interactions and transcriptional control through diverse mechanisms in a variety of tissues. PDX1:SND1 interactions were confirmed in rodent ß cell lines, mouse islets, and human islets. Utilizing CRISPR-Cas9 gene editing technology, we deleted Snd1 from the mouse ß cell lines, which revealed numerous differentially expressed genes linked to insulin secretion and cell proliferation, including limited expression of Glp1r. We observed Snd1 deficient ß cell lines had reduced cell expansion rates, GLP1R protein levels, and limited cAMP accumulation under stimulatory conditions, and further show that acute ablation of Snd1 impaired insulin secretion in rodent and human ß cell lines. Lastly, we discovered that PDX1:SND1 interactions were profoundly reduced in human ß cells from donors with type 2 diabetes (T2D). These observations suggest the PDX1:SND1 complex formation is critical for controlling a subset of genes important for ß cell function and is targeted in diabetes pathogenesis.

Loss of the methylarginine reader function of SND1 confers resistance to hepatocellular carcinoma.

Staphylococcal nuclease Tudor domain containing 1 (SND1) protein is an oncogene that 'reads' methylarginine marks through its Tudor domain. Specifically, it recognizes methylation marks deposited by protein arginine methyltransferase 5 (PRMT5), which is also known to promote tumorigenesis. Although SND1 can drive hepatocellular carcinoma (HCC), it is unclear whether the SND1 Tudor domain is needed to promote HCC. We sought to identify the biological role of the SND1 Tudor domain in normal and tumorigenic settings by developing two genetically engineered SND1 mouse models, an Snd1 knockout (Snd1 KO) and an Snd1 Tudor domain-mutated (Snd1 KI) mouse, whose mutant SND1 can no longer recognize PRMT5-catalyzed methylarginine marks. Quantitative PCR analysis of normal, KO, and KI liver samples revealed a role for the SND1 Tudor domain in regulating the expression of genes encoding major acute phase proteins, which could provide mechanistic insight into SND1 function in a tumor setting. Prior studies indicated that ectopic overexpression of SND1 in the mouse liver dramatically accelerates the development of diethylnitrosamine (DEN)-induced HCC. Thus, we tested the combined effects of DEN and SND1 loss or mutation on the development of HCC. We found that both Snd1 KO and Snd1 KI mice were partially protected against malignant tumor development following exposure to DEN. These results support the development of small molecule inhibitors that target the SND1 Tudor domain or the use of upstream PRMT5 inhibitors, as novel treatments for HCC.

The chromatin architectural regulator SND1 mediates metastasis in triple-negative breast cancer by promoting CDH1 gene methylation.

BACKGROUND: SND1 participates in tumorigenesis, tumour invasion and metastasis in different cancers. Previous studies have shown that SND1 can promote the invasion and migration of breast cancer cells. Triple-negative breast cancer (TNBC) is a specific breast cancer subtype with high metastatic potential and poor prognosis. However, the specific roles and mechanisms of SND1 in TNBC metastasis remain unaddressed. METHODS: Immunostaining was used to detect the SND1 expression in tissue samples of 58 TNBC and 10 glioblastomas (GBM) as positive control. The correlation between SND1 expression and patient prognosis was assessed using the Kaplan-Meier estimator. The gene expression was evaluated by qRT-PCR, Western blot and immunofluorescence analyses. Gene Ontology analysis, ChIP, a dual-luciferase reporter assay, EMSA, and 3C analysis were applied to identify SND1-activated target genes. Bisulfite sequencing PCR and MeDIP were used to detect DNA methylation. We also used wound healing, Transwell and orthotopic implantation assays to investigate the function of SND1 in TNBC cell migration and invasion. RESULTS: The data of immunohistochemistry manifested that SND1 is the overexpression in metastasized TNBC and an independent factor for TNBC prognosis. SND1 knockdown inhibited the migration and invasion of TNBC cells. We found that SND1 promotes the metastatic phenotype of TNBC cells by epigenetically altering chromatin conformational interactions, which in turn activates DNMT3A transcription. Then, DNMT3A attenuates CCND1 expression by inducing CCND1 gene methylation, leading to TNBC metastasis. CONCLUSION: SND1 can promote the invasion and migration of TNBC cells by promoting DNMT3A expression and suppressing CDH1 activity. SND1 is a potential biomarker and a promising therapeutic target for TNBC.

SND1 aggravates mitochondrial damage, apoptosis and extracellular matrix degradation in IL-1ß-stimulated chondrocytes via PINK1/BECN1 pathway.

Recently, evidence has suggested a regulatory role for SND1 in osteoarthritis progression. Interestingly, we found that SND1 protein expression was increased, mitochondria were shrunken and decreased in number, mitochondrial membrane potential was decreased, mitochondrial ROS production was increased, and ATP levels were decreased in IL-1ß treated mouse chondrocytes, and SND1 silencing removed these changes. Furthermore, IL-1ß treatment promoted inflammatory factor secretion in chondrocytes, promoted cell apoptosis, increased MMP13 protein and inhibited collagen II protein expression, and si-SND1 inhibited the IL-1ß effects. We validated the association between SND1 and PINK1 and found that PINK1 reversed the inhibitory effects of SND1 silencing on IL-1ß-induced mitochondrial damage, inflammatory reaction, apoptosis and extracellular matrix degradation in mouse chondrocytes. Furthermore, we found that PINK1 upregulated BECN1 protein expression and that BECN reversed the inhibitory effects of PINK1 silencing on IL-1ß-induced mitochondrial damage, inflammatory reaction, apoptosis and extracellular matrix degradation. Further mechanistic studies revealed that PINK1 inhibited the AMPK/mTOR signaling axis to aggravate IL-1ß induced mouse chondrocytes injury by upregulating BECN1 protein expression. In vivo results showed that the damage to cartilage tissue was significantly alleviated in rats with osteoarthritis by knocking down SND1 expression.

ZNF143 inhibits hepatocyte mitophagy and promotes non-alcoholic fatty liver disease by targeting increased lncRNA NEAT1 expression to activate ROCK2 pathway.

BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) is the most common hepatic disorders worldwide. The mitophagy is suggested to be repressed in NAFLD, but the mechanism remains to be elucidated. METHODS: NAFLD cell and mouse models were established by treating with free fatty acid (FFA) and feeding a high fat diet (HFD), respectively. QRT-PCR, Western blotting, or IHC measured the expression of ZNF143, lncRNA NEAT1, ROCK2, and lipid formation/mitophagy-related proteins. Cell viability and mitophagy were evaluated by MTT and immunofluorescence. The chloroform-methanol extraction method measured triglyceride and total cholesterol levels. ELISA detected ALT and AST levels. The interactions among ZNF143, lncRNA NEAT1 and SND1 were analysed by ChIP, dual-luciferase reporter, pull-down, and RIP. The lipid droplets were determined by Oil-red O and HE staining. RESULTS: ZNF143 and lncRNA NEAT1 were upregulated in hepatic cells treated with FFA (p < 0.01 and p < 0.001). Knockdown of ZNF143 or lncRNA NEAT1 inhibited lipid droplets formation, while promoting mitophagy (p < 0.01 and p < 0.001). ZNF143 promoted lncRNA NEAT1 transcriptional expression through binding to its promoter. LncRNA NEAT1 increased ROCK2 mRNA stability by targeting SND1. LncRNA NEAT1 or ROCK2 overexpression reversed the effect of ZNF143 or lncRNA NEAT1 knockdown on hepatic steatosis and mitophagy (p < 0.01 and p < 0.001). ZNF143 or lncRNA NEAT1 knockdown inhibited HFD-induced steatosis and promoted mitophagy in vivo (p < 0.01 and p < 0.001). CONCLUSION: The upregulation of lncRNA NEAT1 caused by ZNF143 promoted NAFLD through inhibiting mitophagy via activating ROCK2 pathway by targeting SND1, providing potential targets for NAFLD therapy.

SND1, a novel co-activator of HIF1α, promotes tumor initiation in PyMT-induced breast tumor.

The multifunctional protein staphylococcal nuclease domain-containing protein 1 (SND1) is conserved and has been implicated in several aspects of tumor development, such as proliferation, epithelial-mesenchymal transition, and immune evasion. Despite this, the precise role of SND1 in the initiation and metastasis of mammary gland tumors remains largely unexplored. In this study, we utilized a mouse model of breast tumors induced by polyomavirus middle T antigen (PyMT) to demonstrate that the knockout of SND1 significantly delayed the onset of primary mammary tumor formation induced by PyMT. Histological staining and cytometric analysis were conducted to confirm the reduction of tumor-initiating cells and lung metastasis following depletion of SND1. Additionally, our findings demonstrate that enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2), a crucial epigenetic modifier implicated in PyMT-induced breast tumors, serves as an essential mediator of SND1-promoted primary mammary tumor formation. Mechanistic investigations revealed that SND1 functions as a transcriptional co-activator of hypoxia-inducible factor 1 subunit alpha (HIF1α), thereby regulating the downstream target gene EZH2 and promoting tumorigenesis. Overall, this study provides novel insights into the role of SND1 as a co-activator of HIF1α in the acceleration of PyMT-induced spontaneous breast tumor formation through the promotion of EZH2 transcription. The findings provide novel insights into the relationship between SND1 and the formation of tumor-initiating cells.

Exploring binding modes of the selected inhibitors to SND1 by all-atom molecular dynamics simulations.

Breast cancer is the leading cause of cancer-related deaths in women. Previous studies have indicated that disrupting the interaction between Metadherin (MTDH) and Staphylococcal nuclease domain containing 1 (SND1) can inhibit breast cancer development. Understanding the binding mode of small molecule inhibitors with SND1 is of great significance for designing drugs targeting the MTDH-SND1 complex. In this study, we conducted all-atom molecular dynamics (MD) simulations in solution and performed binding energy calculations to gain insights into the binding mechanism of small molecules to SND1. The binding site of SND1 for small molecules is relatively rigid, and the binding of the small molecule and the mutation of key residues have little effect on the conformation of the binding site. SND1 binds more tightly to C26-A6 than to C26-A2, as C26-A2 undergoes a 180° directional change during the simulation process. The key residue mutations have a direct effect on the position and orientation of small molecule in the binding site. The key residues make primary contributions to the binding energy through van der Waals interaction and nonpolar solvation energy, although the contribution from nonpolar solvation is relatively minor. The key residue mutations also affect the formation of hydrogen bonds and ultimately the stability of the small molecule-SND1 complex.Communicated by Ramaswamy H. Sarma.

The RNA-binding protein Snd1/Tudor-SN regulates hypoxia-responsive gene expression.

Snd1 is an evolutionarily conserved RNA-binding protein implicated in several regulatory processes in gene expression including activation of transcription, mRNA splicing, and microRNA decay. Here, we have investigated the outcome of Snd1 gene deletion in the mouse. The knockout mice are viable showing no gross abnormalities apart from decreased fertility, organ and body size, and decreased number of myeloid cells concomitant with decreased expression of granule protein genes. Deletion of Snd1 affected the expression of relatively small number of genes in spleen and liver. However, mRNA expression changes in the knockout mouse liver showed high similarity to expression profile in adaptation to hypoxia. MicroRNA expression in liver showed upregulation of the hypoxia-induced microRNAs miR-96 and -182. Similar to Snd1 deletion, mimics of miR-96/182 enhanced hypoxia-responsive reporter activity. To further elucidate the function of SND1, BioID biotin proximity ligation assay was performed in HEK-293T cells to identify interacting proteins. Over 50% of the identified interactors were RNA-binding proteins, including stress granule proteins. Taken together, our results show that in normal growth conditions, Snd1 is not a critical factor for mRNA transcription in the mouse, and describe a function for Snd1 in hypoxia adaptation through negatively regulating hypoxia-related miRNAs and hypoxia-induced transcription consistent with a role as stress response regulator.

ELFN1-AS1 promotes GDF15-mediated immune escape of colorectal cancer from NK cells by facilitating GCN5 and SND1 association.

The ability of colorectal cancer (CRC) cells to escape from natural killer (NK) cell immune surveillance leads to anti-tumor treatment failure. The long non-coding RNA (lncRNA) ELFN1-AS1 is aberrantly expressed in multiple tumors suggesting a role as an oncogene in cancer development. However, whether ELFN1-AS1 regulates immune surveillance in CRC is unclear. Here, we determined that ELFN1-AS1 enhanced the ability of CRC cells to escape from NK cell surveillance in vitro and in vivo. In addition, we confirmed that ELFN1-AS1 in CRC cells attenuated the activity of NK cell by down-regulating NKG2D and GZMB via the GDF15/JNK pathway. Furthermore, mechanistic investigations demonstrated that ELFN1-AS1 enhanced the interaction between the GCN5 and SND1 protein and this influenced H3k9ac enrichment at the GDF15 promotor to stimulate GDF15 production in CRC cells. Taken together, our findings indicate that ELFN1-AS1 in CRC cells suppresses NK cell cytotoxicity and ELFN1-AS1 is a potential therapeutic target for CRC.

Circular RNA METTL9 contributes to neuroinflammation following traumatic brain injury by complexing with astrocytic SND1.

BACKGROUND: Circular RNAs (circRNAs) are highly enriched in the central nervous system and have been implicated in neurodegenerative diseases. However, whether and how circRNAs contribute to the pathological processes induced by traumatic brain injury (TBI) has not been fully elucidated. METHODS: We conducted a high-throughput RNA sequencing screen for well-conserved, differentially expressed circRNAs in the cortex of rats subjected to experimental TBI. Circular RNA METTL9 (circMETTL9) was ultimately identified as upregulated post-TBI and further characterized by RT-PCR and agarose gel electrophoresis, Sanger sequencing, and RNase R treatment. To examine potential involvement of circMETTL9 in neurodegeneration and loss of function following TBI, circMETTL9 expression in cortex was knocked-down by microinjection of a shcircMETTL9 adeno-associated virus. Neurological functions were evaluated in control, TBI, and TBI-KD rats using a modified neurological severity score, cognitive function using the Morris water maze test, and nerve cell apoptosis rate by TUNEL staining. Pull-down assays and mass spectrometry were conducted to identify circMETTL9-binding proteins. Co-localization of circMETTL9 and SND1 in astrocytes was examined by fluorescence in situ hybridization and immunofluorescence double staining. Changes in the expression levels of chemokines and SND1 were estimated by quantitative PCR and western blotting. RESULTS: CircMETTL9 was significantly upregulated and peaked at 7 d in the cerebral cortex of TBI model rats, and it was abundantly expressed in astrocytes. We found that circMETTL9 knockdown significantly attenuated neurological dysfunction, cognitive impairment, and nerve cell apoptosis induced by TBI. CircMETTL9 directly bound to and increased the expression of SND1 in astrocytes, leading to the upregulation of CCL2, CXCL1, CCL3, CXCL3, and CXCL10, and ultimately to enhanced neuroinflammation. CONCLUSION: Altogether, we are the first to propose that circMETTL9 is a master regulator of neuroinflammation following TBI, and thus a major contributor to neurodegeneration and neurological dysfunction.

Identification of Small Inhibitors for Human Metadherin, an Oncoprotein, through in silico Approach.

AIMS: Cancer is a disease that takes lives of thousands of people each year. There are more than 100 different types of cancers known to man. This fatal disease is one of the leading causes of death today. BACKGROUND: Astrocyte elevated gene-1(AEG-1)/Metadherin (MTDH) activates multiple oncogenic signaling pathways and leads to different types of cancers. MTDH interacting with staphylococcal nuclease domain containing 1(SND1) supports the survival and growth of mammary epithelial cells under oncogenic conditions. OBJECTIVE: Silencing MTDH or SND1 individually or disrupting their interaction compromises the tumorigenic potential of tumor-initiating cells. The aim of our present study was to investigate novel interactions of staphylococcal nuclease domain containing 1 (SND1) binding domain of AEG-1/MTDH with different lead compounds through molecular docking approach using MOE software. METHODS: Molecular docking was done by docking the ChemBridge database against important residues of MTDH involved in interaction with SND1. After docking the whole ChemBridge database, the top 200 interactive compounds were selected based on docking scores. After applying Lipinski's rule, all the remaining chosen compounds were studied on the basis of binding affinity, binding energy, docking score and protein-ligand interactions. Finally, 10 compounds showing multiple interactions with different amino acid residues were selected as the top interacting compounds. RESULTS: Three compounds were selected for simulation studies after testing these compounds using topkat toxicity and ADMET studies. The simulation study indicated that compound 32538601 is a lead compound for inhibiting MTDH-SND1 complex formation. CONCLUSION: These novels, potent inhibitors of MTDH-SND1 complex can ultimately help us in controlling cancer up to some extent.

lncRNA SND1-IT1 delivered via intracerebral hemorrhage-derived exosomes affect the growth of human microglia by regulating the miR-124-3p/MTF1 axis.

In this study, we investigated the effects of long noncoding RNA (lncRNA) SND1-IT1 on human microglia (HMC3 cells) delivered by intracerebral hemorrhage (ICH)-derived exosomes (ICH-exos) as well as a competitive endogenous RNA (ceRNA) network. Exosomes obtained from ICH plasma were characterized by nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), and western blot. RNA sequencing was performed to study the lncRNA transcriptome from ICH-exos and the healthy control-derived exosomes (HC-exos) and differentially expressed lncRNAs (DE-lncRNAs) were identified. HMC3 cells were treated with ICH-exos or transfected with pcDNA3.1-SND1-IT1, and then cell viability and apoptosis were measured. The ceRNA network (lncRNA SND1-IT1/miR-124-3p/messenger RNA MTF1) was chosen for further investigation. NTA, TEM, and western blot showed that exosomes were successfully separated and could be absorbed by HMC3 cells. The expression of lncRNA SND1-IT1 in ICH-exos was significantly higher than that of HC-exos (p < 0.05). In addition, lncRNA SND1-IT1 overexpression and ICH-exos significantly inhibited cell viability and enhanced apoptosis. A total of 162 DE-lncRNAs were identified by sequencing, and a ceRNA network was constructed. The dual-luciferase reporter gene indicated that lncRNA SND1-IT1, miR-124-3p, and MTF1 interacted with each other. Cell experiments showed that lncRNA SND1-IT1 affected the growth of HMC3 cells through miR-124-3p/MTF1. In conclusion, ICH-exos delivered lncRNA SND1-IT1 to HMC3 cells, and exosomal lncRNA SND1-IT1 can regulate cell viability and apoptosis to influence HMC3 cell growth via the SND1-IT1/miR-124-3p/MTF1 axis.