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.

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.

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.

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 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.

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.

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.

SND1 acts as a functional target of miR-330-5p involved in modulating the proliferation, apoptosis and invasion of colorectal cancer cells.

MicroRNAs (miRNAs) play a crucial role in cancer progression due to their capability to modulate the expression of various target genes. However, given the heterogeneity of tumor cells, miRNAs have been confirmed to exert different regulatory effects. Here, bioinformatic analysis results indicated that expression of miR-330-5p is decreased in colorectal cancer (CRC) tissues and inversely correlated with SND1 expression. Notably, ectopic expression of miR-330-5p restrained tumor cell proliferation, migration, and enhance the sensitivity of CRC cells to 5-FU. Moreover, similar phenotypes were substantiated after inhibition of SND1 expression using RNA interference. Conversely, overexpression of SND1 facilitated the malignant phenotypes of CRC cells and restored miR-330-5p-mediated tumor-suppressive activities in CRC cells. Mechanistically, miR-330-5p directly binds to SND1-3'-untranslated region (3'-UTR), thus involving in inhibiting CRC cells proliferation and invasion and promoting apoptosis. Taken together, miR-330-5p may act as a tumor suppressor by targeting the expression of SND1, suggesting that the miR-330-5p/SND1 axis may be a meaningful regulator for CRC intervention.

Exosome-mediated lncRNA SND1-IT1 from gastric cancer cells enhances malignant transformation of gastric mucosa cells via up-regulating SNAIL1.

BACKGROUND: Gastric cancer (GC), as one of the most common malignancies across the globe, is the fourth leading cause of cancer-related deaths. Though a large body of research has been conducted to develop the therapeutic methods of GC, the survival rate of advanced patients is still poor. We aimed to dig into the potential regulatory mechanism of GC progression. METHODS: Bioinformatics tools and fundamental assays were performed at first to confirm the candidate genes in our study. The functional assays and mechanism experiments were conducted to verify the regulatory mechanisms of the genes underlying GC progression. RESULTS: Long non-coding RNA (lncRNA) SND1 intronic transcript 1 (SND1-IT1) is highly expressed in exosomes secreted by GC cells. SND1-IT1 was verified to bind to microRNA-1245b-5p (miR-1245b-5p) through competitive adsorption to promote ubiquitin specific protease 3 (USP3) messenger RNA (mRNA) expression. SND1-IT1 was validated to recruit DEAD-box helicase 54 (DDX54) to promote USP3 mRNA stability. SND1-IT1 induces malignant transformation of GES-1 cells through USP3. USP3 mediates the deubiquitination of snail family transcriptional repressor 1 (SNAIL1). CONCLUSIONS: Exosome-mediated lncRNA SND1-IT1 from GC cells enhances malignant transformation of GES-1 cells via up-regulating SNAIL1.

The RNA-binding protein SND1 promotes the degradation of GPX4 by destabilizing the HSPA5 mRNA and suppressing HSPA5 expression, promoting ferroptosis in osteoarthritis chondrocytes.

BACKGROUND: Heat shock protein family A member 5 (HSPA5), a recently identified suppressor of ferroptosis, was reported to potentially regulating osteoarthritis. However, the exact role of HSPA5 and how its expression was regulated in osteoarthritis are largely unclear. METHODS: Rat primary chondrocytes were treated with 10 ng/mL IL-1ß for 24 h and incubated with ferrostatin-1 (a ferroptosis inhibitor). Cell viability, production of TNF-α, ROS and MDA, expression levels of collagen II, MMP13, GPX4, and SND1, and Fe2+ concentration were detected. Gain- and loss-of-function manipulations were performed to investigate the effect of HSPA5 on chondrocyte functions, and SND1 shRNA (sh-SND1) was transfected into IL-1ß-treated primary chondrocytes alone or together with sh-HSPA5. Furthermore, the interaction between HSPA5 and GPX4 and the regulation of HSPA5 on GPX4 were explored. Finally, SND1 was knocked down in the rats with osteoarthritis, and the histopathology, expression of HSPA5-GPX4 axis, and levels of oxidative stress markers were evaluated. RESULTS: IL-1ß treatment could enhance extracellular matrix (ECM) degradation (collagen II reduced and MMP13 increased), promote ferroptosis, manifested by decreased cell viability, increased levels of TNF-α, ROS, MDA, and Fe2+ concentrations, and decreased level of GPX4 protein, and increase SND1 expression in chondrocytes, which could be reversed by ferrostatin-1. Knockdown of SND1 enhanced ECM degradation and suppressed ferroptosis IL-1ß-treated chondrocytes, which could be eliminated by knockdown of HSPA5. SND1 bound with HSPA5 at the 3'UTR and destabilized the HSPA5 mRNA. HSPA5 protein directly bound with GPX4 protein and positively regulate its expression. HSPA5 overexpression suppressed IL-1ß-induced chondrocyte ferroptosis, while this effect was counteracted by GPX4 silencing. Knockdown of SND1 upregulated HSPA5 and GPX4 in rat cartilage, inhibited inflammatory damage and ferroptosis, and alleviated OA progression. CONCLUSION: The RNA-binding protein SND1 promotes the degradation of GPX4 by destabilizing the HSPA5 mRNA and suppressing HSPA5 expression, promoting ferroptosis in osteoarthritis chondrocytes.

PAX5 activates telomerase activity and proliferation in keloid fibroblasts by transcriptional regulation of SND1, thus promoting keloid growth in burn-injured skin.

OBJECTIVE: Staphylococcal nuclease domain-containing 1 (SND1) that functioned as an oncogene in a variety of tumors was upregulated in burn-injured skin tissues, and this study aims to investigate the effect of SND1 on keloid and elucidate the underlying mechanism. METHODS: Keloid fibroblasts (KFs) and normal skin fibroblasts (NFs) were isolated from the keloid tissues and adjacent normal skin tissues of keloid patients. The SND1 expression was assessed in keloid tissues and KFs with Western blot assay. Gain- and loss-of-function experiments were performed to investigate the role of SND1 in proliferation, colony formation, telomerase activity, expression of fibrogenic genes and production of pro-inflammatory factors in KFs. Chromatin immunoprecipitation (CHIP) and Dual-luciferase reporter gene assays were used to verify the interaction of Paired-box gene 5 (PAX5) on SND1 promoter. Then, a series of rescue experiments were performed to verify the effects of SND1 overexpression on PAX5 knockdown-mediated KF functions. Finally, the role of SND1 in keloid formation in vivo was validated in mice with keloid implantation. RESULTS: SND1 was upregulated in keloid tissues and KFs. SND1 positively regulated proliferation, colony formation, telomerase activity, production of pro-inflammatory factors and expression of fibrogenic genes. PAX5 directly bound to the SND1 promoter to transcriptionally regulate SND1 expression and positively regulated SND1-mediated KF functions via the ERK/JNK pathway. In vivo assay further demonstrated that SND1 displayed a positive effect on keloid formation. CONCLUSION: SND1 transcriptionally regulated by PAX5 promotes keloid formation through activating telomerase activity via the ERK/JNK signaling pathways, which provides a promising therapeutic target for clinical treatment of burned skin keloid.

SND1 facilitates the invasion and migration of cervical cancer cells by Smurf1-mediated degradation of FOXA2.

Staphylococcal nuclease domain-containing protein 1 (SND1) is known to be involved in the progression of a variety of human cancers. However, the role of SND1 in cervical cancer remains unclear. Here, we found that the expression of SND1 in cervical cancer tissue was higher than that in normal cervical tissue. Importantly, high SND1 expression was closely associated with tumorigenic phenotype and shorter survival among cervical cancer patients. Functional assays demonstrated that SND1 knockdown inhibited the migration and invasion capabilities of cervical cancer cells in vitro. Additionally, a xenograft assay showed that silencing SND1 in cervical cancer cells suppressed lung metastasis in vivo. Further investigation revealed that knockdown of SND1 inhibited epithelial-to-mesenchymal transition (EMT) of cervical cancer cells by enhancing FOXA2 expression. Moreover, the pro-metastasis effect of SND1 in cervical cancer was at least in part dependent on FOXA2 inhibition. Mechanistically, we found that SND1-induced FOXA2 ubiquitination resulted in degradation, mediated by the E3 ligase enzyme Smurf1. In summary, SND1 plays a crucial role in cervical cancer metastasis, and we provide evidence that SND1 may serve as a prognostic and therapeutic target in cervical cancer.

A pan-cancer analysis of the oncogenic role of staphylococcal nuclease domain-containing protein 1 (SND1) in human tumors.

Although emerging cell- or animal-based evidence supports the relationship between SND1 and cancers, no pan-cancer analysis is available. We thus first explored the potential oncogenic roles of SND1 across thirty-three tumors based on the datasets of TCGA (The cancer genome atlas) and GEO (Gene expression omnibus). SND1 is highly expressed in most cancers, and distinct associations exist between SND1 expression and prognosis of tumor patients. We observed an enhanced phosphorylation level of S426 in several tumors, such as breast cancer or lung adenocarcinoma. SND1 expression was associated with the CD8+T-cell infiltration level in colon adenocarcinoma and melanoma, and cancer-associated fibroblast infiltration was observed in other tumors, such as bladder urothelial carcinoma or testicular germ cell tumors. Moreover, protein processing- and RNA metabolism-associated functions were involved in the functional mechanisms of SND1. Our first pan-cancer study offers a relatively comprehensive understanding of the oncogenic roles of SND1 across different tumors.

Gene fusion characterisation of rare aggressive prostate cancer variants-adenosquamous carcinoma, pleomorphic giant-cell carcinoma, and sarcomatoid carcinoma: an analysis of 19 cases.

AIMS: To evaluate the molecular underpinnings of the rare aggressive prostate cancer variants adenosquamous carcinoma, pleomorphic giant-cell carcinoma, and sarcomatoid carcinoma. METHODS AND RESULTS: We retrieved 19 tumours with one or more variant(s), and performed ERG immunohistochemistry, a next-generation sequencing assay targeting recurrent gene fusions, and fluorescence in-situ hybridisation (FISH) for ERG and BRAF. Divergent differentiation included: sarcomatoid carcinoma (n = 10), adenosquamous carcinoma (n = 7), and pleomorphic giant-cell carcinoma (n = 7). Five patients had more than one variant. Four had variants only in metastases. ERG rearrangement was detected in nine (47%, seven via sequencing, showing TMPRSS2-ERG fusions and one GRHL2-ERG fusion, and two via FISH, showing rearrangement via deletion). ERG was immunohistochemically positive in the adenocarcinoma in eight of nine (89%) patients, but was immunohistochemically positive in the variant in only five of nine patients (56%, typically decreased). One patient had a false-positive ERG immunohistochemical result in the sarcomatoid component despite a negative FISH result. Two (11%) harboured BRAF fusions (FAM131A-BRAF and SND1-BRAF). CONCLUSIONS: ERG fusions are present in these rare prostate cancer variants with a frequency close to that in conventional prostate cancer (9/19, 47%). ERG immunohistochemistry usually detects rearrangement in the adenocarcinoma, but is less sensitive for the variant histology, with weak to negative staining. Adenosquamous and sarcomatoid variants can, particularly, occur together. Molecular assessment may be an additional tool in selected cases to confirm the prostatic origin of unusual tumours. The presence of two BRAF rearrangements suggests that this gene fusion may be enriched in this setting, as RAF kinase fusions have been previously reported in 1-2% of prostate cancers.

PTB-AS, a Novel Natural Antisense Transcript, Promotes Glioma Progression by Improving PTBP1 mRNA Stability with SND1.

Glioma, the most common primary malignancy in the brain, has high recurrence and lethality rates, and thus, elucidation of the molecular mechanisms of this incurable disease is urgently needed. Poly-pyrimidine tract binding protein (PTBP1, also known as hnRNP I), an RNA-binding protein, has various mechanisms to promote gliomagenesis. However, the mechanisms regulating PTBP1 expression are unclear. Herein, we report a novel natural antisense noncoding RNA, PTB-AS, whose expression correlated positively with PTBP1 mRNA. We found that PTB-AS significantly promoted the proliferation and migration in vivo and in vitro of glioma cells. PTB-AS substantially increased the PTBP1 level by directly binding to its 3' UTR and stabilizing the mRNA. Furthermore, staphylococcal nuclease domain-containing 1 (SND1) dramatically increased the binding capacity between PTB-AS and PTBP1 mRNA. Mechanistically, PTB-AS could mask the binding site of miR-9 in the PTBP1-3' UTR; miR-9 negatively regulates PTBP1. To summarize, we revealed that PTB-AS, which maintains the PTBP1 level through extended base pairing to the PTBP1 3' UTR with the assistance of SND1, could significantly promote gliomagenesis.

[Downregulation of SND1 Expression Accelerates Cell Senescence of Human Diploid Fibroblasts 2BS via Modulating the SASP].

OBJECTIVE: To investigate the effect of down-regulation of SND1 expression on senescence of human diploid fibroblasts. METHODS: Western blot and immunohistochemistry were used to detect the expression of SND1 in young or senescent 2BS cells and aged tissues. Immunofluorescence was conducted to detect the localization of SND1 in young 2BS cells. CCK8 and EDU were performed to detect the proliferation of 2BS. Colony formation analysis was used to evaluate the capacity of colony formation of 2BS. Expression chip and RT-qPCR analysis were performed to detect the change of SASP expression level. ß-galactosidase staining was employed to indicate the senescent 2BS cells. RESULTS: The expression of SND1 in the senescent 2BS cells was significantly down-regulated compared with in the younger 2BS cells, and in human colon adenomas, its expression was also significantly down-regulated compared with in non-lesion colon tissues. In young 2BS, knockdown of SND1 inhibited the proliferation and colony formation of 2BS, and led to stronger senescence-associated beta-galactosidase staining (SA-ß-gal). Expression chip and RT-qPCR analysis indicated that knockdown of SND1 up-regulated the expression of senescence-associated secretory phenotype components (SASP). CONCLUSIONS: Our data indicated that down-regulation of SND1 regulated human diploid cell senescence by up-regulating the expression of SASP components.

Protective effects of SND1 in retinal photoreceptor cell damage induced by ionizing radiation.

Staphylococcal nuclease and tudor domain containing 1 (SND1) has multiple functions in a variety of cellular processes. Here, we assessed the effects of SND1 in cellular DNA damage after ionizing radiation (IR). Knocking down SND1 in the mouse-derived photoreceptor 661 W cell line markedly inhibited cell proliferation and increased apoptosis after IR treatment. After DNA damage, SND1 induced Ataxia telangiectasia mutated kinase (ATM) signaling to launch DNA repair. Defects of SND1 were associated with missing response to DNA damage signal to cell cycle checkpoints or DNA repair. The current findings reveal SND1 as a new regulatory factor in DNA damage response.

LincRNA TINCR facilitates excessive proliferation and inflammation in post-burn skin fibroblasts by directly binding with SND1 protein and inducing SND1-mediated TGF-ß1 expression.

In this study, we found that lincRNA-TINCR was significantly upregulated in burn-injured skin tissues in vivo and heat-stimulated dermal fibroblasts in vitro, accompanied by an increase in TGF-ß1 expression. TINCR overexpression promoted cell proliferation, colony formation, release of pro-inflammatory factors and expression of TGF-ß1 protein in human primary fibroblasts under normal condition. Moreover, silencing TINCR reduced expression of TGF-ß1, cell proliferation, colony formation and inflammation in heat-stressed fibroblasts. Subsequently, motif analysis in TINCR sequence revealed that there were two potential target sites for the RNA-binding protein Staphylococcal Nuclease and Tudor Domain Containing 1 (SND1). We verified their direct binding by using RNA-IP assays using wild-type or mutated biotinylated TINCR transcripts TINCR and demonstrated that TINCR overexpression enhanced the binding of TINCR and SND1. Furthermore, SND1 knockdown improved fibroblast behaviors, like silencing TINCR, and SND1 overexpression could antagonize the effect of silencing TINCR on fibroblast proliferation and inflammation.

Analysis of Orthologous SECONDARY WALL-ASSOCIATED NAC DOMAIN1 (SND1) Promotor Activity in Herbaceous and Woody Angiosperms.

SECONDARY WALL-ASSOCIATED NAC DOMAIN1 (SND1) is a master regulator of fibre secondary wall deposition in Arabidopsis thaliana (Arabidopsis), with homologs in other angiosperms and gymnosperms. However, it is poorly understood to what extent the fibre-specific regulation of the SND1 promoter, and that of its orthologs, is conserved between diverged herbaceous and woody lineages. We performed a reciprocal reporter gene analysis of orthologous SND1 promoters from Arabidopsis (AthSND1), Eucalyptus grandis (EgrNAC61) and Populus alba × P. grandidentata (PagWND1A) relative to secondary cell wall-specific Cellulose Synthase4 (CesA4) and CesA7 promoters, in both a non-woody (Arabidopsis) and a woody (poplar) system. ß-glucuronidase (GUS) reporter analysis in Arabidopsis showed that the SND1 promoter was active in vascular tissues as previously reported and showed interfascicular and xylary fibre-specific expression in inflorescence stems, while reporter constructs of the woody plant-derived promoters were partial to the (pro)cambium-phloem and protoxylem. In transgenic P. tremula × P. alba plants, all three orthologous SND1 promoters expressed the GUS reporter similarly and preferentially in developing secondary xylem, ray parenchyma and cork cambium. Ours is the first study to reciprocally test orthologous SND1 promoter specificity in herbaceous and woody species, revealing diverged regulatory functions in the herbaceous system.

SND1 acts as an anti-apoptotic factor via regulating the expression of lncRNA UCA1 in hepatocellular carcinoma.

Multifunctional SND1 (staphylococcal nuclease and tudor domain containing 1) protein is reportedly associated with different types of RNA molecules, including mRNA, miRNA, pre-miRNA, and dsRNA. SND1 has been implicated in a number of biological processes in eukaryotic cells, including cell cycle, DNA damage repair, proliferation, and apoptosis. However, the specific molecular mechanism regarding the anti-apoptotic role of SND1 in mammalian cells remains largely elusive. In this study, the analysis of the online HPA (human protein atlas) and TCGA (the cancer genome atlas) databases showed the significantly high expression of SND1 in liver cancer patients. We found that the downregulation or complete depletion of SND1 enhanced the apoptosis levels of HepG2 and SMMC-7721 cells upon stimulation with 5-Fu (5-fluorouracil), a chemotherapeutic drug for HCC (hepatocellular carcinoma). SND1 affected the 5-Fu-induced apoptosis levels of HCC cells by modulating the expression of UCA1 (urothelial cancer associated 1), which is a lncRNA (long non-coding RNA). Moreover, MYB (MYB proto-oncogene, transcription factor) may be involved in the regulation of SND1 in UCA1 expression. In summary, our study identified SND1 as an anti-apoptotic factor in hepatocellular carcinoma cells via the modulation of lncRNA UCA1, which sheds new light on the relationship between SND1 protein and lncRNA.