Sumoylation of TCF21 downregulates the transcriptional activity of estrogen receptor-alpha

The Role of SUMO E3 Ligases in Signaling Pathway of Cancer Cells

Small ubiquitin-like modifier (SUMO)ylation is a reversible post-translational modification that plays a crucial role in numerous aspects of cell physiology, including cell cycle regulation, DNA damage repair, and protein trafficking and turnover, which are of importance for cell homeostasis. Mechanistically, SUMOylation is a sequential multi-enzymatic process where SUMO E3 ligases recruit substrates and accelerate the transfer of SUMO onto targets, modulating their interactions, localization, activity, or stability. Accumulating evidence highlights the critical role of dysregulated SUMO E3 ligases in processes associated with the occurrence and development of cancers. In the present review, we summarize the SUMO E3 ligases, in particular, the novel ones recently identified, and discuss their regulatory roles in cancer pathogenesis.

Transcription Factor 21 Promotes Chicken Adipocyte Differentiation at Least in Part via Activating MAPK/JNK Signaling

The molecular mechanisms of transcription factor 21 (TCF21) in regulating chicken adipogenesis remain unclear. Thus, the current study was designed to investigate the signaling pathway mediating the effect of TCF21 on chicken adipogenesis. Immortalized chicken preadipocytes cell line (ICP), a preadipocyte cell line stably overexpressing TCF21 (LV-TCF21) and a control preadipocyte cell line (LV-control) were used in the current study. We found that the phosphorylation of c-Jun N-terminal kinases (JNK) was significantly elevated in LV-TCF21 compared to LV-control. After treating ICP cells with a JNK inhibitor SP600125, the differentiation of ICP was inhibited, as evidenced by decreased accumulation of lipid droplets and reduced expression of peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding protein α (C/EBPα), adipocyte fatty acid binding protein (A-FABP), and lipoprotein lipase (LPL). Moreover, we found that the inhibition of JNK by SP600125 remarkably impaired the ability of TCF21 to drive adipogenesis. Taken together, our results suggest that TCF21 promotes the differentiation of adipocytes at least in part via activating MAPK/JNK pathway.

Role of the bHLH transcription factor TCF21 in development and tumorigenesis

Transcription factors control, coordinate, and separate the functions of distinct network modules spatially and temporally. In this review, we focus on the transcription factor 21 (TCF21) network, a highly conserved basic-helix-loop-helix (bHLH) protein that functions to integrate signals and modulate gene expression. We summarize the molecular and biological properties of TCF21 control with an emphasis on molecular and functional TCF21 interactions. We suggest that these interactions serve to modulate the development of different organs at the transcriptional level to maintain growth homeostasis and to influence cell fate. Importantly, TCF21 expression is epigenetically inactivated in different types of human cancers. The epigenetic modification or activation and/or loss of TCF21 expression results in an imbalance in TCF21 signaling, which may lead to tumor initiation and, most likely, to progression and tumor metastasis. This review focuses on research on the roles of TCF21 in development and tumorigenesis systematically considering the physiological and pathological function of TCF21. In addition, we focus on the main molecular bases of its different roles whose importance should be clarified in future research. For this review, PubMed databases and keywords such as TCF21, POD-1, capsulin, tumors, carcinomas, tumorigenesis, development, and mechanism of action were utilized. Articles were selected within a historical context as were a number of citations from journals with relevant impact.

Increased SUMOylation of TCF21 improves its stability and function in human endometriotic stromal cells†

Endometriosis is an estrogen-dependent disease. Our previous study demonstrated that elevated levels of transcription factor 21 (TCF21) in endometriotic tissues enhanced steroidogenic factor-1 (SF-1) and estrogen receptor β (ERβ) expression by forming a heterodimer with upstream stimulatory factor 2 (USF2), allowing these TCF21/USF2 complexes to bind to the promoters of SF-1 and ERβ. Furthermore, TCF21 contributed to the increased proliferation of endometriotic stromal cells (ESCs), suggesting that TCF21 may play a vital role in the pathogenesis of endometriosis. SUMOylation is a posttranslational modification that has emerged as a crucial molecular regulatory mechanism. However, the mechanism regulating TCF21 SUMOylation in endometriosis is incompletely characterized. Thus, this study aimed to explore the effect of TCF21 SUMOylation on its expression and regulation in ovarian endometriosis. We found that the levels of SUMOylated TCF21 were increased in endometriotic tissues and stromal cells compared with eutopic endometrial tissues and stromal cells and enhanced by estrogen. Treatment with the SUMOylation inhibitor ginkgolic acid and the results of a protein half-life assay demonstrated that SUMOylation can stabilize the TCF21 protein. A coimmunoprecipitation assay showed that SUMOylation probably increased its interaction with USF2. Further analyses elucidated that SUMOylation of TCF21 significantly increased the binding activity of USF2 to the SF-1 and ERβ promoters. Moreover, the SUMOylation motifs in TCF21 affected the proliferation ability of ESCs. The results of this study suggest that SUMOylation plays a critical role in mediating the high expression of TCF21 in ESCs and may participate in the development of endometriosis.

SUMO and Transcriptional Regulation: The Lessons of Large-Scale Proteomic, Modifomic and Genomic Studies

One major role of the eukaryotic peptidic post-translational modifier SUMO in the cell is transcriptional control. This occurs via modification of virtually all classes of transcriptional actors, which include transcription factors, transcriptional coregulators, diverse chromatin components, as well as Pol I-, Pol II- and Pol III transcriptional machineries and their regulators. For many years, the role of SUMOylation has essentially been studied on individual proteins, or small groups of proteins, principally dealing with Pol II-mediated transcription. This provided only a fragmentary view of how SUMOylation controls transcription. The recent advent of large-scale proteomic, modifomic and genomic studies has however considerably refined our perception of the part played by SUMO in gene expression control. We review here these developments and the new concepts they are at the origin of, together with the limitations of our knowledge. How they illuminate the SUMO-dependent transcriptional mechanisms that have been characterized thus far and how they impact our view of SUMO-dependent chromatin organization are also considered.

Transcription factor 21 expression in injured podocytes of glomerular diseases

Transcription factor 21 (TCF21) is one of the essential transcription factors in kidney development. To elucidate its influence on glomerular disease, we have investigated TCF21 expression in human and rat kidney tissue, and its urinary concentration. Immunohistological analysis suggested the highest TCF21 expression in nephrotic syndrome along with the urinary protein level. Urinary TCF21 concentration in human showed a positive correlation with its podocyte expression level. In nephrotic rat models, TCF21 expression in podocytes increased along with the severity of nephrotic syndrome. Next, in vitro experiments using Tcf21-expressing murine podocyte cell line, we could observe some Tcf21-dependent effects, related with actin cytoskeleton dysregulation and apoptosis. Our study illustrated TCF21 expression changes in vivo and its in vitro-functional significance injured podocytes.

PBX1 is a valuable prognostic biomarker for patients with breast cancer

Pre-B-cell leukemia transcription factor (PBX) proteins have important roles in the development of numerous organs. To date, four members of the PBX family have been identified to be involved in human cancer but little is known about their expression patterns and precise functions in breast cancer (BC) progression. The aim of the present study was to determine whether they have the potential to be prognostic biomarkers in patients with BC. The expression patterns of PBXs were evaluated using Oncomine, Cancer Cell Line Encyclopedia and Gene expression-based Outcome for Breast cancer Online algorithm analyses. The prognostic value of PBX1 was determined by Kaplan-Meier plotter analysis. It was observed that, among all PBX family members, only PBX1 was significantly upregulated in BC vs. normal tissues. Meta-analysis in the Oncomine database revealed that PBX1 was significantly upregulated in invasive breast carcinoma stroma, ductal breast carcinoma, invasive lobular breast carcinoma, invasive mixed breast carcinoma and male breast carcinoma compared with normal tissues. In addition, PBX1 was significantly correlated with forkhead box protein A1. Subtype analysis indicated that PBX1 overexpression was associated with luminal-like and hormone receptor-sensitive subtypes. In the survival analysis, a high expression level of PBX1 was associated with poor prognosis of patients with estrogen receptor (ER)-positive, luminal A and luminal B subtypes of BC. The results of the present study indicate that PBX1 may serve as a specific biomarker and essential prognostic factor for ER-positive, luminal A and luminal B subtypes of BC.

TCF21 inhibits proliferation and chemoresistance through the AKT pathway in human gastric cancer

In a previous study, we showed that transcription factor 21 (TCF21) is methylated and downregulated in human gastric cancer samples and serves as an independent prognostic factor. However, its biological role and potential mechanism in gastric cancer cells remain unexplored. In the current study, we examined TCF21 expression in 6 gastric cancer cell lines. The BGC-823 and SGC-7901 cell lines were selected for small interfering RNA and plasmid transfection, respectively. The results of the Cell Counting Kit-8 assay demonstrated that TCF21 inhibited gastric cancer cell proliferation. Cell cycle analysis suggested that TCF21 inhibited cell cycle progression in gastric cancer cells. The Matrigel invasion assay demonstrated that TCF21 negatively regulated invasion. The cell adhesion assay showed that TCF21 increased cell adhesion. Gastric cancer cells were treated with cisplatin to explore the role of TCF21 in chemoresistance. Cell Counting Kit-8 assay and AnnexinV/propidium iodide analyses showed that TCF21 overexpression sensitized SGC-7901 cells to cisplatin, whereas its depletion reduced sensitivity in BGC-823 cells. JC-1 staining was performed to measure the effect of TCF21 on mitochondrial potential. TCF21 downregulated mitochondrial membrane potential after treatment with cisplatin. Western blot analysis showed that TCF21 overexpression negatively regulated Bcl-xL, phosphorylated extracellular signal regulated kinase, and phosphorylated AKT expression and induced caspase 3 cleavage. LY294002, an AKT inhibitor, blocked the effect of TCF21 on Bcl-xL, caspase 3 and CDDP-induced apoptosis. Nude mice experiments demonstrated that TCF21 inhibited gastric cancer growth in vivo. In conclusion, our results suggest that TCF21 inhibits gastric cancer growth and chemoresistance possibly through the AKT signaling pathway.

Transcription factor 21 regulates expression of ERβ and SF-1 via upstream stimulatory factor-2 in endometriotic tissues

Steroidogenic factor-1 (SF-1, encoded by NR5A1) and estrogen receptor beta (ERβ, encoded by ESR2), which are highly expressed in endometriotic stromal cells (ESCs), contribute to the pathogenesis of endometriosis, but the regulation mechanism remains largely unknown. Transcription factor 21 (TCF21) belongs to the helix-loop-helix (bHLH) family characterized by regulating gene expression via binding to E-box element. Here, we attempted to determine the molecular mechanism of TCF21 on SF-1 and ERβ expression in endometriosis. We found that TCF21 expression in ESCs was higher than that in endometrial stromal cells (EMs), and positively correlated with SF-1 and ERβ expression in ESCs. Since the importance of E-box element for NR5A1 promoter activity has been previously reported, we performed site-mutation and luciferase assay, revealing that the E-box sequence in the ESR2 promoter is also a critical element modulating ERβ expression. Upstream stimulatory factor 2 (USF2) is another bHLH factor implicated in transcriptional regulation. Further analyses elucidated that it is not TCF21, but USF2 exhibited higher binding affinities in ESCs to NR5A1 and ESR2 promoters than in EMs. Additionally, TCF21 knockdown significantly decreased the binding activities of USF2 to NR5A1 and ESR2 promoters via disruption of the TCF21-USF2 complex. Meanwhile, manipulating TCF21 expression significantly affected MMP9 and cyclinD1 expression, as wells as proliferation and invasion of ESCs. Moreover, TCF21 depletion in endometriotic xenografts reduced SF-1 and ERβ expression, abrogating ectopic lesion growth in mice. Cumulatively, a critical role of TCF21 in the pathogenesis of endometriosis is demonstrated, suggesting a potential druggable target for future therapy.

Multiple biological functions of transcription factor 21 in the development of various cancers

Transcription factor 21 (TCF21) is a basic helix–loop–helix transcription factor that binds to DNA and regulates cell differentiation and cell fate specification through mesenchymal–epithelial transition during development. The TCF21 gene is epigenetically inactivated in many types of human cancers and exerts a wide variety of functions, including the regulation of epithelial–mesenchymal transition, invasion, metastasis, cell cycle, and autophagy. This review focuses on research progress in relation to the roles of TCF21 in tumor development. We systematically consider multiple pathological functions of TCF21 in various cancers, revealing the molecular bases of its diverse biological roles and providing new directions for future research.

Checkpoint suppressor 1 suppresses transcriptional activity of ERα and breast cancer cell proliferation via deacetylase SIRT1

Breast cancer is a highly heterogeneous carcinoma in women worldwide, but the underlying mechanisms that account for breast cancer initiation and development have not been fully established. Mounting evidence indicates that Checkpoint suppressor 1 (CHES1) is tightly associated with tumorigenesis and prognosis in many types of cancer. However, the definitive function of CHES1 in breast cancer remains to be explored. Here we showed that CHES1 had a physical interaction with estrogen receptor-α (ERα) and repressed the transactivation of ERα in breast cancer cells. Mechanistically, the interaction between CHES1 and ERα enhanced the recruitment of nicotinamide adenine dinucleotide (NAD+) deacetylase Sirtuin 1 (SIRT1), and it further induced SIRT1-mediated ERα deacetylation and repression on the promoter-binding enrichment of ERα. In addition, we also found that the expression of CHES1 was repressed by estrogen-ERα signaling and the expression level of CHES1 was significantly downregulated in ERα-positive breast cancer. The detailed mechanism was that ERα may directly bind to CHES1 potential promoter via recognizing the conserved estrogen response element (ERE) motif in response to estrogen stimulation. Functionally, CHES1 inhibited ERα-mediated proliferation and tumorigenesis of breast cancer cells in vivo and in vitro. Totally, these results identified a negative cross-regulatory loop between ERα and CHES1 that was required for growth of breast cancer cells, it might uncover novel insight into molecular mechanism of CHES1 involved in breast cancer and provide new avenues for molecular-targeted therapy in hormone-regulated breast cancer.

α-catenin SUMOylation increases IκBα stability and inhibits breast cancer progression

α-catenin has been demonstrated to suppress several different types of cancers. Here we demonstrate that α-catenin is modified by SUMO protein, which covalently binds α-catenin at the carboxy terminus at lysine 870. Substitution of lysine 870 with arginine completely abolishes α-catenin SUMOylation. This modification can be removed by SENP1. However, α-catenin SUMOylation does not affect its stability and subcellular localization. In addition, we observed that the SUMOylation-deficient α-catenin mutant has a reduced interaction with IκBα which prevents subsequent ubiquitination of IκBα, and therefore a reduced suppression of expression of the NF-κB target genes TNF-α, IL-8, VEGF, and uPA. In addition, the α-catenin SUMOylation mutant shows impaired suppression of tumor growth. These results demonstrate that SUMOylation at lysine 870 of α-catenin plays a key role in the suppression of the NF-κB pathway, which inhibits breast cancer tumor growth and migration.

SYNJ2BP promotes the degradation of PTEN through the lysosome-pathway and enhances breast tumor metastasis via PI3K/AKT/SNAI1 signaling

SYNJ2BP plays an important role in breast cancer metastasis. However, the molecular mechanism associated with the function of SYNJ2BP in metastasis remains unclear. In this study, we investigated the role of SYNJ2BP in tumor metastasis and established the associated underlying mechanism. Over-expression of SYNJ2BP promoted both cell migration and invasion. In contrast, silencing SYNJ2BP caused the suppression of cell migration and invasion. SYNJ2BP increased the levels of phosphorylation for AKT and GSK3β, which could be inhibited by the PI3K inhibitor, LY294002, and the GSK3β inhibitor, LiCl, and regulated the accumulation of SNAI1 in the nucleus and the expression of the SNAI1 target gene, E-cadherin (EMT marker). It is known that the stability of PTEN is regulated by ubiquitination. However, in this study, we additionally demonstrated that SYNJ2BP mediated the degradation of PTEN protein by the lysosome-pathway and induced the activation of PI3K/AKT signaling by promoting the co-localization of PTEN with autophagy-lysosomes and the expression of LC3-II and p62. In vivo study, the overexpression of SYNJ2BP significantly increased the metastasis of 4T1 cells in BALB/c mice. In addition, SYNJ2BP was highly expressed in breast carcinoma (p = 0.0031), but not in normal breast tissue, while analysis of tissue samples taken from SNAI1-positive human breast cancers showed a significant correlation between the expression of SYNJ2BP and that of p-AKT (p < 0.005). Collectively, our data identified a tumor inducer, SYNJ2BP, which could activate the PI3K/AKT/GSK3β/SNAI1 signaling pathway through the lysosome-mediated degradation of PTEN, and promote both EMT and tumor metastasis during the progression of breast cancer.