Yin Yang 1 Protein Research Articles

Picroside Ⅱ alleviates renal fibrosis through YY1-dependent transcriptional inhibition of TGFβ1

Diabetic Nephropathy (DN) has become the leading cause of end-stage renal disease worldwide. Studies have indicated that Transforming Growth Factor beta1 (TGFβ1) is the most potent factor contributing to renal fibrosis, and understanding the exact pathogenic mechanism of renal fibrosis is crucial for alleviating the condition. Previous research has identified Yin Yang 1 (YY1) as an effective inhibitor of TGF-β1. Our study, through dual-luciferase reporter gene assays and Western blot experiments, screened and obtained the small molecule compound PdⅡ. Subsequently, validation in a high-glucose-induced renal mesangial cell injury model showed that PdⅡ treatment significantly increased the expression of YY1 protein and mRNA, while correspondingly reducing the expression of TGFβ1 protein and mRNA. Dual-luciferase reporter gene assay results revealed that, compared to the control group, the luciferase transcription activity of YY1 molecules increased in the PdⅡ treatment group, and the luciferase transcription activity of TGFβ1 decreased. By further designing mutations in the binding sites between TGFβ1 and YY1 on the promoter, transfecting fluorescent enzyme reporter gene plasmids with TGFβ1 mutant promoter into mesangial cells damaged by high glucose, and then treating the cells with PdⅡ, it was observed that the luciferase transcription activity of TGFβ1 did not decrease. Therefore, these results suggest that PdⅡ may inhibit TGFβ1 transcriptional activity by activating YY1, thereby slowing down the progression of diabetic nephropathy.

Phosphorylation-dependent deubiquitinase OTUD3 regulates YY1 stability and promotes colorectal cancer progression

Yin Yang 1 (YY1) is a key transcription factor that has been implicated in the development of several malignancies. The stability of YY1 is regulated by the ubiquitin-proteasome system. The role of deubiquitinases (DUBs) and their impact on YY1 remain to be fully elucidated. In this study, we screened for ubiquitin-specific proteases that interact with YY1, and identified OTUD3 as a DUB for YY1. Over-expressed OTUD3 inhibited YY1 degradation, thereby increasing YY1 protein levels, whereas OTUD3 knockdown or knockout promoted YY1 degradation, thereby decreasing the proliferation of colorectal cancer (CRC). Furthermore, PLK1 mediates OTUD3 S326 phosphorylation, which further enhances OTUD3 binding and deubiquitination of YY1. In CRC tissues, elevated the expression level of OTUD3 and YY1 were significantly associated with poor prognostic outcomes. These findings suggest that the OTUD3-YY1 pathway has therapeutic potential in CRC, and OTUD3 plays a critical role in regulating YY1.

Yin Yang 1 promotes the neuroendocrine differentiation of prostate cancer cells via the non-canonical WNT pathway (FYN/STAT3).

A growing number of studies have shown that Yin Yang 1 (YY1) promotes the development of multiple tumours. The purpose of the current study was to determine the mechanism by which YY1 mediates neuroendocrine differentiation of prostate cancer (NEPC) cells undergoing cellular plasticity. Using the Cancer Genome Atlas and Gene Expression Omnibus (GEO) databases, we bioinformatically analyzed YY1 expression in prostate cancer (PCa). Aberrant YY1 expression was validated in different PCa tissues and cell lines via quantitative reverse transcription polymerase chain reaction, western blotting, and immunohistochemistry. In vivo and in vitro functional assays verified the oncogenicity of YY1 in PCa. Further functional assays showed that ectopic expression of YY1 promoted cellular plasticity in PCa cells via epithelial-mesenchymal transition induction and neuroendocrine differentiation. Androgen deprivation therapy induced a decrease in YY1 protein ubiquitination, enhanced its stability, and thus enhanced the transcriptional activity of FZD8. Castration enhanced FZD8 binding to Wnt9A and mediated cellular plasticity by activating the non-canonical Wnt (FZD8/FYN/STAT3) pathway. We identified YY1 as a novel dysregulated transcription factor that plays an important role in NEPC progression in this study. We believe that an in-depth investigation of the mechanism underlying YY1-mediated disease may lead to improved NEPC therapies.

Downregulation of MicroRNA-29-3p Following Percutaneous Coronary Intervention: An Implication of YY1/IRAK1 Pathway in the Post-Vascular Injury Inflammation.

This study explored the expression of microRNA (miR)-29b-3p following percutaneous coronary intervention (PCI) and the implication of its downstream Yin Yang 1 (YY1)/interleukin (IL)-1 receptor-associated kinase 1 (IRAK1) pathway in post-vascular injury inflammation. Blood samples were collected for analysis of plasma miR-29b-3p from patients with acute coronary syndrome before surgery, 1 day after PCI, and 30 days after PCI. Lipopolysaccharide (LPS)-treated human coronary artery endothelial cells (HCAECs) were transfected with miR-29b-3p mimic/inhibitor or YY1 shRNA and underwent viability tests. Enzyme-linked immunosorbent assay was performed to detect the levels of soluble vascular cell adhesion molecule-1 (sVCAM-1), IL-1β, IL-6, and tumor necrosis factor (TNF)-α in serum and cell culture supernatant. Dual-luciferase reporter and RNA/chromatin immunoprecipitation were used to confirm the targeting relationships among miR-29b-3p, YY1, and IRAK1. A rat model of intraluminal injury of the common femoral artery was established to address the role of miR-29b-3p and relevant mechanisms. miR-29b-3p was lowly expressed, and sVCAM-1, IL-1β, IL-6, and TNF-α were upregulated 1 day after PCI and 24 h after LPS treatment. miR-29b-3p overexpression or YY1 knockdown alleviated LPS-induced inflammatory responses and improved the viability of HCAECs. miR-29b-3p inhibition aggravated LPS-induced inflammatory injury in HCAECs. miR-29b-3p bound to YY1 mRNA and inhibited the expression of YY1 protein. YY1 bound to the IRAK1 promoter and activated the transcription of IRAK1. Upregulation of miR-29b-3p suppressed the inflammatory response after intraluminal injury of the common femoral artery in rats. In conclusion, dysregulation of the YY1/IRAK1 pathway via miR-29b-3p downregulation may be implicated in post-vascular injury inflammation.

Prognostic Implication of YY1 and CP2c Expression in Patients with Primary Breast Cancer.

Yin Yang 1 (YY1) is a transcription factor that regulates epigenetic pathways and protein modifications. CP2c is a transcription factor that functions as an oncogene to regulate cell proliferation. YY1 is known to interact with CP2c to suppress CP2c's transcriptional activity. This study aimed to investigate YY1 and CP2c expression in breast cancer and prognostic implications. In this study, YY1 and CP2c expression was evaluated using immunohistochemical staining, Western blot and RT-PCR assays. Of 491 patients with primary breast cancer, 138 patients showed YY1 overexpression. Luminal subtype and early stage were associated with overexpression (p < 0.001). After a median follow-up of 68 months, YY1 overexpression was found to be associated with a better prognosis (disease-free survival rates of 92.0% vs. 79.2%, p = 0.014). In Cox proportional hazards model, YY1 overexpression functioned as an independent prognostic factor after adjustment of hormone receptor/HER2 status and tumor size (hazard ratio of 0.50, 95% CI 0.26-0.98, p = 0.042). Quantitative analysis of YY1 and CP2c protein expression in tumors revealed a negative correlation between them. In conclusion, YY1 overexpression is a favorable prognostic biomarker in patients with breast cancer, and it has a negative correlation with CP2c at the protein level.

USP8 mitigates cognitive dysfunction of mice with sepsis-associated encephalopathy.

Sepsis-associated encephalopathy (SAE) is a serious complication of sepsis which results from neuroinflammation and could lead to cognitive dysfunction. Ubiquitin-specific peptidase 8 (USP8) is involved in cognitive dysfunction. This study investigated the mechanism by which USP8 plays a role in cognitive dysfunction of SAE mice. The SAE models were established by performing cecal ligation and puncture in the mice. Subsequently, a series of tests and procedures were conducted to assess the cognitive dysfunction and pathological impairment of mice, including the Morris water maze test, Y-maze test, open field test, tail suspension test, fear conditioning test, and haematoxylin-eosin staining. The levels of USP8 and Yin Yang 1 (YY1) in brain tissues of mice were detected. In order to determine the effects of USP8 or YY1 on cognitive function, SAE mice were injected with an adenovirus-packaged vector that had overexpressed levels of USP8 or YY1 short hairpin RNA. The binding of USP8 to YY1 and the ubiquitination level of YY1 were analyzed using immunoprecipitation and ubiquitination experiments. Lastly, chromatin immunoprecipitation was carried out to analyze enrichment of YY1 on the USP8 promoter. In SAE models, USP8 and YY1 were downregulated and cognitive functions were impaired. USP8 overexpression upregulated YY1 and attenuated the brain histopathological damage and cognitive dysfunction in SAE mice. USP8 upregulated YY1 protein level through deubiquitination, while YY1 was enriched on the USP8 promoter and activated USP8 transcription. The effects of USP8 overexpression on SAE mice was reversed secondary to YY1 silencing. USP8 upregulated YY1 protein level through deubiquitination and YY1 activated USP8 transcription, and USP8-YY1 feedback loop attenuated cognitive dysfunction in SAE mice, which could potentially serve as a novel theoretical foundation for the management of SAE.

The role of transcription factor Yin Yang-1 in colorectal cancer.

Yin Yang-1 (YY1) is identified as a transcription factor with multiple functions. However, the role of YY1 in tumorigenesis remains controversial and its regulatory effects may depend upon not only cancer types, but also its interacting partners, chromatin structure, and the context in which it acts. It has been detected that YY1 was highly expressed in colorectal cancer (CRC). Intriguingly, many YY1-repressed genes exhibit tumor suppressive potential while YY1 silencing is related to chemotherapy resistance. Therefore, it is crucial to meticulously explore YY1 protein structure and the dynamic alteration of its interactome in each cancer type. This review attempts to describe the structure of YY1, summarize the mechanism that influence the expression level of YY1 and also highlight the recent advances in our understanding of regulatory insights of YY1 functions in CRC. Related studies were identified through scoping search of PubMed, Web of science, Scopus and Emhase concerning the terms of "colorectal cancer", colorectal carcinoma" or CRC with "YY1". The retrieval strategy included title, abstract, and keywords with no language limitations. All the included articles were categorized depending on the mechanisms they explored. In total, 170 articles were identified for further screening. After removing the duplication, not relevant outcomes and review articles, 34 were finally included in the review. Among them, 10 articles revealed the reasons of YY1 high expression in CRC, 13 articles explored YY1 function in CRC, and 11 articles fell into both aspects. In addition, we also summarized 10 clinical trials concerning the expression and activity of YY1 in various diseases, which offers a hint for future application. YY1 is highly expressed in CRC and broadly recognized as an oncogenic factor during the whole course of CRC. Sporadic controversial views are raised in term of CRC treatment, reminding us that future studies should take the influence of therapeutic regimens into concern.

YY1 Oligomerization Is Regulated by Its OPB Domain and Competes with Its Regulation of Oncoproteins.

Simple SummaryYY1 regulates various cancer-related genes and activates key oncoproteins. In this study, we discovered that the oncoprotein binding (OPB) domain of YY1 is both necessary and stimulatory to its oligomerization. The hydrophobic residues, especially F219, in the OPB are essential to YY1 intermolecular interaction. Strikingly, the mutations of the hydrophobic residues showed better ability than wild-type YY1 in promote breast cancer cell proliferation and migration. Our further study revealed that YY1 proteins with mutated hydrophobic residues in the OPB domain showed improved binding affinity to EZH2. Overall, our data support the model of a mutually exclusive process between oligomerization of YY1 and its regulation of the oncoproteins EZH2, AKT and MDM2.Yin Yang 1 (YY1) plays an oncogenic role through regulating the expression of various cancer-related genes and activating key oncoproteins. Previous research reported that YY1 protein formed dimers or oligomers without definite biological implications. In this study, we first demonstrated the oncoprotein binding (OPB) and zinc finger (ZF) domains of YY1 as the regions involved in its intermolecular interactions. ZFs are well-known for protein dimerization, so we focused on the OPB domain. After mutating three hydrophobic residues in the OPB to alanines, we discovered that YY1(F219A) and YY1(3A), three residues simultaneously replaced by alanines, were defective of intermolecular interaction. Meanwhile, the OPB peptide could robustly facilitate YY1 protein oligomerization. When expressed in breast cancer cells with concurrent endogenous YY1 knockdown, YY1(F219A) and (3A) mutants showed better capacity than wt in promoting cell proliferation and migration, while their interactions with EZH2, AKT and MDM2 showed differential alterations, especially with improved EZH2 binding affinity. Our study revealed a crucial role of the OPB domain in facilitating YY1 oligomerization and suggested a mutually exclusive regulation between YY1-mediated enhancer formation and its activities in promoting oncoproteins.

Enhanced Sp1/YY1 Expression Directs CBS Transcription to Mediate VEGF-Stimulated Pregnancy-Dependent H2S Production in Human Uterine Artery Endothelial Cells.

[Figure: see text].

YY1 Promotes Telomerase Activity and Laryngeal Squamous Cell Carcinoma Progression Through Impairment of GAS5-Mediated p53 Stability

Yin Yang 1 (YY1) is a key transcription factor that exerts functional roles in the cell biological process of various cancers. The current study aimed to elucidate the role and mechanism of YY1 in laryngeal squamous cell carcinoma (LSCC). YY1 mRNA and protein expression in human LSCC cell lines was detected by RT-qPCR and Western blot analysis. An interaction of YY1, GAS5, and p53 protein stability was predicted and confirmed by bioinformatics, ChIP, Co-IP, RIP, and FISH assays. Following loss- and gain-function assays, LSCC cell proliferation, colony formation, cell cycle, telomere length and telomerase activity were evaluated by CCK-8 assay, colony formation assay, flow cytometry, and PCR-ELISA, respectively. Nude mice were xenografted with the tumor in vivo. LSCC cell lines presented with upregulated expression of YY1, downregulated GAS5 expression, and decreased p53 stability. YY1 inhibited the expression of GAS5, which in turn recruited p300 and bound to p53, thus stabilizing it. Moreover, YY1 could directly interact with p300 and suppressp53 stability, leading to enhancement of cell proliferation, telomere length and telomerase activity in vitro along with tumor growth in vivo. Collectively, YY1 can stimulate proliferation and telomerase activity of LSCC cells through suppression of GAS5-dependent p53 stabilization or by decreasing p53 stability via a direct interaction with p300, suggesting that YY1 presents a therapeutic target as a potential oncogene in LSCC development and progression.

Disruption of YY1-EZH2 Interaction Using Synthetic Peptides Inhibits Breast Cancer Development.

Simple SummaryBoth Yin Yang 1 (YY1) and enhancer of zeste homolog 2 (EZH2) are oncogenes with overexpressed statuses in cancers. As a transcription factor, YY1 recruits EZH2 through its oncoprotein binding (OPB) domain to repress gene expression. In this study, we identified the interaction domain of YY1 on EZH2 protein with amino acids 493–519, named the YY1 protein binding (YPB) domain. Synthetic peptides using YPB and OPB domain sequences effectively blocked endogenous YY1-EZH2 interaction. Functionally, YPB and OPB peptides could efficiently inhibit the proliferation of breast cancer cells, promote their apoptosis, and reduce tumor growth in a xenograft mouse model. Using chromatin immunoprecipitation DNA sequencing (ChIP-seq) analysis, we discovered that YPB and OPB peptides could interfere with H3K27 trimethylation of multiple genes. Eventually, we identified that YPB and OPB peptides primarily targeted the PTENP1 gene and validated its importance in the anticancer activity of the two peptides.Enhancer of zeste homolog 2 (EZH2) is a methyltransferase to mediate lysine 27 trimethylation in histone H3 (i.e., H3K27me3) and repress gene expression. In solid tumors, EZH2 promotes oncogenesis and is considered a therapeutic target. As a transcription factor, Yin Yang 1 (YY1) recruits EZH2 through its oncoprotein binding (OPB) domain to establish gene repression. In this study, we mapped the YY1 protein binding (YPB) domain on EZH2 to a region of 27 amino acids. Both YPB and OPB domain synthetic peptides could disrupt YY1EZH2 interaction, markedly reduce breast cancer cell viability, and efficiently inhibit tumor growth in a xenograft mouse model. We analyzed MDA-MB-231 cells treated with YPB, OPB, and control peptides by chromatin immunoprecipitation DNA sequencing (ChIP-seq) using an antibody against H3K27me3. YPB and OPB treatments altered H3K27me3 on 465 and 1137 genes, respectively, compared to the control. Of these genes, 145 overlapped between the two peptides. Among them, PTENP1, the PTEN pseudogene, showed reduced H3K27me3 signal when treated by either YPB or OPB peptide. Consistently, the two peptides enhanced both PTENP1 and PTEN expression with concomitantly reduced AKT activation. Further studies validated PTENP1′s contribution to the anticancer activity of YPB and OPB peptides.

YY1-mediated PTEN dephosphorylation antagonizes IR-induced DNA repair contributing to tongue squamous cell carcinoma radiosensitization

Ionizing radiation (IR) confers a survival advantage in tongue squamous cell carcinoma (TSCC), however, IR resistance limits its efficacy. Although Yin Yang 1 (YY1) has been reported to play a role in genotoxic drug resistance by accelerating DNA repair, its role in TSCC radioresistance remains unclear. In this study, we examined YY1 mRNA and protein expression in human tongue cancer samples using qRT-PCR and western blotting, respectively. DNA array data identified YY1 mRNA expression in IR sensitivity or resistance cell lines and tissues. Tongue carcinoma primary cells and CAL27 cells with YY1 stably overexpressed or knocked-down were exposed to IR and evaluated for cell proliferation and apoptosis by CCK8-assay and caspase-3 assay, respectively. We also examined DNA damage- or repair-related indicators, such as YY1, p-H2AX, nuclear PTEN, p-PTEN, and Rad51 through Western blot analysis. Additionally, we explored the mechanism of IR-induced PTEN nuclear translocation by introducing a series of PTEN phosphorylation site mutations and co-IP assay. We observed that YY1 mRNA and protein are highly expressed in TSCC tissues, which was correlated with worse overall survival. Moreover, higher expression of YY1 and Rad51 was observed in radioresistant cells and tissues, overexpression of YY1 led to IR resistance in TSCC cells, whereas YY1 knockdown sensitized TSCC cells to IR. The underlying mechanism showed that the overexpression of YY1 upregulated nuclear PTEN and Rad51 expression, which is essential for DNA repair. IR upregulated YY1, nuclear PTEN, and Rad51; thus, knockdown of YY1 completely blocked IR-induced upregulation of nuclear PTEN/Rad51. IR upregulated PTEN phosphorylation, and mutation of the phosphorylation site of Ser380 nearly completely blocked IR-induced PTEN nuclear translocation. Furthermore, the phosphatase PP2A negatively regulated pS380-PTEN, and knockdown of YY1 completely blocked IR-induced pS380-PTEN through PP2A. In conclusion, knockdown of YY1 enhanced TSCC radiosensitivity through PP2A-mediated dephosphorylation of PTEN Ser380; thus, antagonizing the IR-induced nuclear PTEN/Rad51 axis and targeting YY1 may reverse IR resistance in TSCC.

Yin Yang-1 suppresses CD40 ligand-CD40 signaling-mediated anti-inflammatory cytokine interleukin-10 expression in pulmonary adventitial fibroblasts by promoting histone H3 tri-methylation at lysine 27 modification on interleukin-10 promoter.

During the pathogenesis of early pulmonary arterial hypertension (PAH), pulmonary arterial adventitial fibroblast act as an initiator and mediator of inflammatory processes that predispose vessel walls to excessive vasoconstriction and pathogenic vascular remodeling. Emerging studies report that Yin Yang-1 (YY-1) plays important roles in inflammatory response and vascular injury. Our recent study finds that activation of CD40 ligand (CD40L)-CD40 signaling promotes pro-inflammatory phenotype of pulmonary adventitial fibroblasts. However, whether YY-1 is involved in CD40L-CD40 signaling-triggered inflammatory response in pulmonary adventitial fibroblasts and its underlying mechanism is still unclear. Here, we show that soluble CD40L (sCD40L) stimulation promotes YY-1 protein expression and suppresses anti-inflammatory cytokine, interleukin 10 (IL-10) expression in pulmonary adventitial fibroblasts, while YY-1 knockdown prevents sCD40L-mediated reduction of IL-10 expression via enhancing IL-10 gene transactivation. Further, we find that sCD40L stimulation significantly increases histone H3 tri-methylation at lysine 27 (H3K27me3) modification on IL-10 promoter in pulmonary adventitial fibroblasts, and YY-1 knockdown prevents the effect of sCD40L on IL-10 promoter by reducing the interaction with enhancer of zeste homolog 2 (EZH2), a histone methyltransferase, binding to IL-10 promoter. Moreover, we find that sCD40L stimulation promotes YY-1 protein, but not messenger RNA (mRNA) expression, via decreasing N6-methyladenosine methylation on YY-1 mRNA to suppress YTHDF2-medicated mRNA decay. Overall, this in-depth study shows that the activation of CD40L-CD40 signaling upregulates YY-1 protein expression in pulmonary adventitial fibroblasts, which results in increasing YY-1 and EZH2 binding to the IL-10 promoter region to enhance H3K27me3 modification, eventually leading to suppression of IL-10 transactivation. This study first uncovers the roles of YY-1 on CD40L-CD40 signaling-triggered inflammatory response in pulmonary adventitial fibroblasts.

Heat shock cognate protein 70 promotes the differentiation of C2C12 myoblast and targets Yin Yang 1.

Heat shock cognate protein 70 (HSC70) is a constitutively expressed molecular chaperone protein which can maintain the structure and function of the protein. HSC70 is engaged in a variety of physiological processes, yet its role during skeletal muscle differentiation is still unclear. C2C12 cells were obtained and cultured. During differentiation, the expression of HSC70 was evaluated by RT-PCR. To determine the function of HSC70 during C2C12 myoblast differentiation, myotube transfection of siR-HSC70 was performed with Lipofectamine 2000 Reagent. Western blot was used to measure the expression of Yin Yang 1 (YY1) after down-regulating HSC70. To further assess if YY1 mediates the pro-differentiation effect of HSC70, a plasmid of YY1 overexpression was used to increase the expression of YY1 in the presence of siR-HSC70-2. The formation of myotubes was visualized by immunofluorescent staining, while the expression levels of MyoD and MyoG were evaluated by RT-PCR. In this study, we found that HSC70 was up-regulated during C2C12 myoblast differentiation. Knockdown of HSC70 not only inhibited the C2C12 myoblast differentiation but also reduced the expression of MyoD and MyoG. When YY1 protein was over-expressed, it could restore the differentiation in cells with HSC70 knockdown or inhibition. Collectively, this study demonstrates that HSC70 is involved in the regulation of C2C12 myoblast differentiation via YY1 and may serve as a potential target for a therapeutic strategy to prevent muscle atrophy.

Planar cell polarity gene Fuz triggers apoptosis in neurodegenerative disease models.

Planar cell polarity (PCP) describes a cell-cell communication process through which individual cells coordinate and align within the plane of a tissue. In this study, we show that overexpression of Fuz, a PCP gene, triggers neuronal apoptosis via the dishevelled/Rac1 GTPase/MEKK1/JNK/caspase signalling axis. Consistent with this finding, endogenous Fuz expression is upregulated in models of polyglutamine (polyQ) diseases and in fibroblasts from spinocerebellar ataxia type 3 (SCA3) patients. The disruption of this upregulation mitigates polyQ-induced neurodegeneration in Drosophila We show that the transcriptional regulator Yin Yang 1 (YY1) associates with the Fuz promoter. Overexpression of YY1 promotes the hypermethylation of Fuz promoter, causing transcriptional repression of Fuz Remarkably, YY1 protein is recruited to ATXN3-Q84 aggregates, which reduces the level of functional, soluble YY1, resulting in Fuz transcriptional derepression and induction of neuronal apoptosis. Furthermore, Fuz transcript level is elevated in amyloid beta-peptide, Tau and α-synuclein models, implicating its potential involvement in other neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. Taken together, this study unveils a generic Fuz-mediated apoptotic cell death pathway in neurodegenerative disorders.

BCCIP binds to and activates its promoter in a YY1-dependent fashion in HCT116 cells.

The restriction of Yin Yang 1 (YY1) at BRCA2 and CDKN1A/p21-interacting protein (BCCIP) transcriptional start site (TSS) proximal region in several human cancer cell lines was found by analyzation of ChIP-Seq database from UCSC Genome Browser (http://genome.ucsc.edu). However, whether the stabilization of YY1 by BCCIP impacts its recruitment in the BCCIP promoter region is unclear. Here, we present evidence that transcriptional regulation of YY1 on BCCIP is closely related to YY1 stability in HCT116 human colon cancer cells. YY1 stabilization was in turn regulated by BCCIP, suggesting the existence of a BCCIP-YY1 feedback loop in regulating BCCIP transcription by the YY1. Overexpression of BCCIP stabilized YY1 while knockdown of BCCIP reduced YY1 protein level. In addition, direct interaction between YY1 and BCCIP was confirmed by coimmunoprecipitation approach. Also, the N-terminus region of BCCIP, including the internal conserved domain (ICD), was responsible for binding with the amino acid 146-270 of YY1. More importantly, YY1 stability was related to the BCCIP/ICD domain-mediated YY1 ubiquitination pathway. Moreover, a limited BCCIP promoter region containing YY1 binding site (CCGCCATC) was tightly associated with the pGL4-BCCIP-Luc luciferase activity. In ChIP assays, shBCCIP lentiviral-mediated YY1 instability decreased recruitment of the YY1 at BCCIP TSS proximal region, which could not be restored by YY1 overexpression. Furthermore, knockdown of YY1 inhibited the binding of BCCIP itself at BCCIP promoter region proximal to TSS, demonstrating that transcriptional regulation of the YY1 on BCCIP can be modulated by BCCIP itself in a YY1-dependent fashion.

Knockdown of Yin Yang 1 enhances anticancer effects of cisplatin through protein phosphatase 2A-mediated T308 dephosphorylation of AKT

Cisplatin is still one of the first-line drugs for chemotherapy of head and neck squamous cell carcinoma (HNSCC) and shows a survival advantage for HNSCC. However, a substantial proportion of HNSCC eventually becomes resistance to cisplatin and the underlying mechanisms remain to be fully understood. Yin Yang 1 (YY1) is a multifunctional protein regulating both gene transcription and protein modifications and also plays a role in chemotherapy resistance. Here, we reported that knockdown of YY1 by lentivirus-mediated short hairpin RNA or tetracycline-inducible short hairpin RNA enhanced cisplatin-induced apoptosis and inhibition of cell proliferation, migration and invasion in the HNSCC cell lines, and inhibition of the xenograft tumor growth. The underlying mechanisms were revealed that knockdown of YY1 downregulated both S473 and T308 phosphorylation of AKT (protein kinase B), which was mainly responsible for cisplatin resistance, whereas overexpression of YY1 upregulated both S473 and T308 phosphorylation. Cisplatin upregulated YY1 mRNA and protein expression and both S473 and T308 phosphorylation of AKT. In the presence of cisplatin, knockdown of YY1 not only blocked cisplatin-induced increase in S473 and T308 phosphorylation of AKT, but still downregulated T308 phosphorylation. Moreover, protein phosphatase 2A (PP2A) antagonist, okadaic acid, upregulated T308, but not S473, phosphorylation, and simultaneously abolished YY1 knockdown-mediated enhancement of cisplatin-induced inhibition of cell proliferation. In addition, knockdown of YY1 promoted PP2A activity through upregulating mRNA and protein expressions of PP2A catalytic subunit alpha (PPP2CA) through the binding of YY1 in the promoter of PPP2CA. Conversely, activating PP2A by forskolin also promoted YY1 degradation and subsequently inhibited T308 phosphorylation. These results suggested that knockdown of YY1 enhanced anticancer effects of cisplatin through PP2A mediating T308 dephosphorylation of AKT, and that targeting YY1 or PP2A would enhance the efficiency of cisplatin chemotherapy in treatment of HNSCC.

YinYang1 deficiency ameliorates joint inflammation in a murine model of rheumatoid arthritis by modulating Th17 cell activation

Yin Yang 1 (YY1) is a ubiquitously expressed transcription factor that functions in cooperation with various cofactors to regulate gene expression. In the immune system, YY1 enhances cytokine production and T helper (Th) 2 effector cell differentiation, resulting in the activation of inflammation. However, no studies have reported the role of YY1 in Th17 cell regulation, which is implicated in rheumatoid arthritis (RA). We investigated the expression of YY1 in Th17 cells in vitro and revealed increased levels of YY1 mRNA and protein. To elucidate the function of YY1 pathogenesis in RA, we used a collagen-induced arthritis (CIA) mouse model with YY1 deficiency. Deficiency of YY1 reduced the severity of arthritis and joint destruction. Moreover, Th17 cells were dramatically reduced in YY1-deficient mice. The cytokine interleukin (IL)-17 was decreased in YY1-deficient CD4+ T cells ex vivo and in vivo. Interestingly, the level of signal transducer and activator of transcription 3 (STAT3), tumor necrosis factor-α, IL-17, IL-6, and IL-1β were markedly decreased in YY1-deficient mice with CIA. The cytokine-inducing function of YY1 was more specific to IL-17 than to interferon-γ. YY1 plays a role in Th17 cell differentiation and RA pathogenesis. Our findings suggest that future RA therapies should target the regulatory mechanism involved in Th17 cell differentiation, in which YY1 may cooperate with the STAT3 signaling pathway.

YY1 Positively Regulates Transcription by Targeting Promoters and Super-Enhancers through the BAF Complex in Embryonic Stem Cells.

SummaryYin Yang 1 (YY1) regulates early embryogenesis and adult tissue formation. However, the role of YY1 in stem cell regulation remains unclear. YY1 has a Polycomb group (PcG) protein-dependent role in mammalian cells. The PcG-independent functions of YY1 are also reported, although their underlying mechanism is still undefined. This paper reports the role of YY1 and BAF complex in the OCT4-mediated pluripotency network in mouse embryonic stem cells (mESCs). The interaction between YY1 and BAF complex promotes mESC proliferation and pluripotency. Knockdown of Yy1 or Smarca4, the core component of the BAF complex, downregulates pluripotency markers and upregulates several differentiation markers. Moreover, YY1 enriches at both promoter and super-enhancer regions to stimulate transcription. Thus, this study elucidates the role of YY1 in regulating pluripotency through its interaction with OCT4 and the BAF complex and the role of BAF complex in integrating YY1 into the core pluripotency network.

YY1 Is a Structural Regulator of Enhancer-Promoter Loops

There is considerable evidence that chromosome structure plays important roles in gene control, but we have limited understanding of the proteins that contribute to structural interactions between gene promoters and their enhancer elements. Large DNA loops that encompass genes and their regulatory elements depend on CTCF-CTCF interactions, but most enhancer-promoter interactions do not employ this structural protein. Here, we show that the ubiquitously expressed transcription factor Yin Yang 1 (YY1) contributes to enhancer-promoter structural interactions in a manner analogous to DNA interactions mediated by CTCF. YY1 binds to active enhancers and promoter-proximal elements and forms dimers that facilitate the interaction of these DNA elements. Deletion of YY1 binding sites or depletion of YY1 protein disrupts enhancer-promoter looping and gene expression. We propose that YY1-mediated enhancer-promoter interactions are a general feature of mammalian gene control.