Yin Yang 1 promotes mTORC2-mediated AKT phosphorylation

Leishmania regulates host YY1: Comparative proteomic analysis identifies infection modulated YY1 dependent proteins

The protein Yin-Yang 1 (YY1) is a ubiquitous multifunctional transcription factor. Interestingly, there are several cellular functions controlled by YY1 that could play a role in Leishmania pathogenesis. Leishmaniasis is a human disease caused by protozoan parasites of the genus Leishmania. This study examined the potential role of macrophage YY1 in promoting Leishmania intracellular survival. Deliberate knockdown of YY1 resulted in attenuated survival of Leishmania in infected macrophages, suggesting a role of YY1 in Leishmania persistence. Biochemical fractionation studies revealed Leishmania infection caused redistribution of YY1 to the cytoplasm from the nucleus where it is primarily located. Inhibition of nuclear transport by leptomycin B attenuates infection-mediated YY1 redistribution and reduces Leishmania survival. This suggests that Leishmania induces the translocation of YY1 from the nucleus to the cytoplasm of infected cells, where it may regulate host molecules to favour parasite survival. A label-free quantitative whole proteome approach showed that the expression of a large number of macrophage proteins was dependent on the YY1 level. Interestingly, several of these proteins were modulated in Leishmania-infected cells, revealing YY1-dependent host response and suggesting their potential role in Leishmania pathogenesis. Together, this study identifies YY1 as a novel virulence factor that promotes Leishmania survival inside host macrophages.

IL-6 Affects Liver Metabolic Abnormalities Caused by Silicon Exposure by Regulating the PKC/YY1 Signaling Pathway

BACKGROUND

This study aims to investigate the impact of coal dust (silicon dioxide) exposure on dyslipidemia and its underlying mechanisms, with a focus on the association between coal dust exposure and hepatic metabolic disorders.

METHODS

Clinical data were collected from 5433 coal mine workers to compare the incidence of dyslipidemia between the dust-exposed group and the non-exposed group. A mouse model of silicon dioxide exposure was established to observe hepatic fat accumulation and pathological changes. Liver tissue sequencing was performed to screen for key differential genes. In vitro cell experiments were utilized to identify the molecular mechanisms underlying hepatocyte metabolic abnormalities induced by silicon dioxide exposure.

RESULTS

Clinical data revealed that 69.2% of miners in the dust-exposed group developed dyslipidemia, which was higher than the 30.7% in the non-exposed group. Animal data showed that silicon dioxide exposure led to hepatic fat deposition and pathological damage, with the degree of injury positively correlated with exposure time. Liver sequencing identified a significant upregulation of the FMO3 (flavin monooxygenase 3) gene in mouse liver tissue following silicon dioxide exposure, accompanied by enhanced inflammatory responses. Mechanistic studies demonstrated that silicon dioxide activates Kupffer cells to secrete IL-6 (interleukin-6), which induces high expression of FMO3 in hepatocytes through the PKC/YY1 signaling pathway, thereby disrupting lipid metabolism.

CONCLUSIONS

Silicon dioxide exposure can promote the upregulation of FMO3 expression in hepatocytes by activating Kupffer cells to release IL-6 via the PKC/YY1 pathway, ultimately leading to lipid metabolic disorders and dyslipidemia.

Transketolase promotes osteosarcoma progression through the YY1-PAK4 axis

Osteosarcoma, a malignant bone tumor that occurs in adolescents, proliferates and is prone to pulmonary metastasis. Osteosarcoma is characterized by high genotypic heterogeneity, making it difficult to identify reliable anti-osteosarcoma targets. The genotype of osteosarcoma may be highly dynamic, but its high dependence on energy remains constant. Fortunately, tumors tend to have relatively consistent metabolic types. Targeting metabolism with anti-tumor therapies is a new strategy for treating tumors. Genes related to carbohydrate metabolism are widely and highly expressed in tumor tissues. Transketolase (TKT), a key enzyme at the non-oxidative stage of the pentose phosphate pathway, is up-regulated in various tumors. In the present study, TKT promoted osteosarcoma cell proliferation non-metabolically. Specifically, TKT bound directly to amino acid residues of Yin Yang 1 (YY1) at amino acids 201-228, stimulating YY1 to bind to the promoter of P21 activated kinase 4 (PAK4) and resulting in PAK4 expression and activation of the phosphoinositide 3-kinase-Akt signaling pathway. Additionally, we designed a peptide, YY1-PEP, based on the exact mechanism of how TKT promotes osteosarcoma. Per in vivo and in vitro experiments, YY1-PEP displayed anti-osteosarcoma properties. The present study provides a new feasible strategy against osteosarcoma progression.

Yin Yang 1 expression predicts a favourable survival in diffuse large B-cell lymphoma

Aims

Yin Yang 1 (YY1) is a multifunctional transcription factor that plays an important role in tumour development and progression, while its clinical significance in diffuse large B-cell lymphoma (DLBCL) remains largely unexplored. This study aimed to investigate the expression and clinical implications of YY1 in DLBCL.

Methods

YY1 expression in 198 cases of DLBCL was determined using immunohistochemistry. The correlation between YY1 expression and clinicopathological parameters as well as the overall survival (OS) and progression-free survival (PFS) of patients was analyzed.

Results

YY1 protein expression was observed in 121 out of 198 (61.1 %) DLBCL cases. YY1 expression was significantly more frequent in cases of the GCB subgroup than in the non-GCB subgroup (P = 0.005). YY1 was positively correlated with the expression of MUM1, BCL6, pAKT and MYC/BCL2 but was negatively associated with the expression of CXCR4. No significant relationships were identified between YY1 and clinical characteristics, including age, sex, stage, localization, and B symptoms. Univariate analysis showed that the OS (P = 0.003) and PFS (P = 0.005) of patients in the YY1-negative group were significantly worse than those in the YY1-positive group. Multivariate analysis indicated that negative YY1 was a risk factor for inferior OS (P < 0.001) and PFS (P = 0.017) independent of the international prognostic index (IPI) score, treatment and Ann Arbor stage. Furthermore, YY1 is more powerful for stratifying DLBCL patients into different risk groups when combined with MYC/BCL2 double-expression (DE) status.

Conclusions

YY1 was frequently expressed in DLBCL, especially in those of GCB phenotype and with MYC/BCL2-DE. As an independent prognostic factor, YY1 expression could predict a favourable outcome in DLBCL. In addition, a complex regulatory mechanism might be involved in the interactions between YY1 and MYC, pAKT as well as CXCR4 in DLBCL, which warrants further investigation.

Clinical Potential of YY1-Hypoxia Axis for Vascular Normalization and to Improve Immunotherapy

Abnormal vasculature in solid tumors causes poor blood perfusion, hypoxia, low pH, and immune evasion. It also shapes the tumor microenvironment and affects response to immunotherapy. The combination of antiangiogenic therapy and immunotherapy has emerged as a promising approach to normalize vasculature and unlock the full potential of immunotherapy. However, the unpredictable and redundant mechanisms of vascularization and immune suppression triggered by tumor-specific hypoxic microenvironments indicate that such combination therapies need to be further evaluated to improve patient outcomes. Here, we provide an overview of the interplay between tumor angiogenesis and immune modulation and review the function and mechanism of the YY1-HIF axis that regulates the vascular and immune tumor microenvironment. Furthermore, we discuss the potential of targeting YY1 and other strategies, such as nanocarrier delivery systems and engineered immune cells (CAR-T), to normalize tumor vascularization and re-establish an immune-permissive microenvironment to enhance the efficacy of cancer therapy.

Zinc Ions Modulate YY1 Activity: Relevance in Carcinogenesis

YY1 is widely recognized as an intrinsically disordered transcription factor that plays a role in development of many cancers. In most cases, its overexpression is correlated with tumor progression and unfavorable patient outcomes. Our latest research focusing on the role of zinc ions in modulating YY1's interaction with DNA demonstrated that zinc enhances the protein's multimeric state and affinity to its operator. In light of these findings, changes in protein concentration appear to be just one element relevant to modulating YY1-dependent processes. Thus, alterations in zinc ion concentration can directly and specifically impact the regulation of gene expression by YY1, in line with reports indicating a correlation between zinc ion levels and advancement of certain tumors. This review concentrates on other potential consequences of YY1 interaction with zinc ions that may act by altering charge distribution, conformational state distribution, or oligomerization to influence its interactions with molecular partners that can disrupt gene expression patterns.

Targeting Transcription Factor YY1 for Cancer Treatment: Current Strategies and Future Directions

Cancer represents a significant and persistent global health burden, with its impact underscored by its prevalence and devastating consequences. Whereas numerous oncogenes could contribute to cancer development, a group of transcription factors (TFs) are overactive in the majority of tumors. Targeting these TFs may also combat the downstream oncogenes activated by the TFs, making them attractive potential targets for effective antitumor therapeutic strategy. One such TF is yin yang 1 (YY1), which plays crucial roles in the development and progression of various tumors. In preclinical studies, YY1 inhibition has shown efficacy in inhibiting tumor growth, promoting apoptosis, and sensitizing tumor cells to chemotherapy. Recent studies have also revealed the potential of combining YY1 inhibition with immunotherapy for enhanced antitumor effects. However, clinical translation of YY1-targeted therapy still faces challenges in drug specificity and delivery. This review provides an overview of YY1 biology, its role in tumor development and progression, as well as the strategies explored for YY1-targeted therapy, with a focus on their clinical implications, including those using small molecule inhibitors, RNA interference, and gene editing techniques. Finally, we discuss the challenges and current limitations of targeting YY1 and the need for further research in this area.

PLAU is associated with cell migration and invasion and is regulated by transcription factor YY1 in cervical cancer

Cervical cancer, one of the most common malignancies, has a poor survival rate. The identification of more biomarkers for cervical cancer diagnosis and therapy is urgently needed. Plasminogen activator urokinase (PLAU) exerts multiple biological effects in various physiological and pathological processes; however the role of PLAU in cervical cancer progression is not fully understood. In the present study, the involvement and transcriptional regulation of PLAU in cervical cancer were explored. The expression of PLAU in cervical cancer was first analyzed, and PLAU was found to be overexpressed. In vitro experiments demonstrated that the migration and invasion of HeLa and HT3 cells were significantly suppressed by PLAU knockdown. Additionally, the core promoter of PLAU was confirmed, and the transcription factor YinYang 1 (YY1) was found to regulate PLAU mRNA expression. Overall, the present study elucidated the direct association between PLAU and cervical cancer, suggesting the YY1/PLAU axis as a potential novel therapeutic target for cervical cancer.

A histidine cluster determines YY1-compartmentalized coactivators and chromatin elements in phase-separated enhancer clusters

As an oncogenic transcription factor, Yin Yang 1 (YY1) regulates enhancer and promoter connection. However, gaps still exist in understanding how YY1 coordinates coactivators and chromatin enhancer elements to assemble enhancers and super-enhancers. Here, we demonstrate that a histidine cluster in YY1’s transactivation domain is essential for its formation of phase separation condensates, which can be extended to additional proteins. The histidine cluster is also required for YY1-promoted cell proliferation, migration, clonogenicity and tumor growth. YY1-rich nuclear puncta contain coactivators EP300, BRD4, MED1 and active RNA polymerase II, and colocalize with histone markers of gene activation, but not that of repression. Furthermore, YY1 binds to the consensus motifs in the FOXM1 promoter to activate its expression. Wild-type YY1, but not its phase separation defective mutant, connects multiple enhancer elements and the FOXM1 promoter to form an enhancer cluster. Consistently, fluorescent in situ hybridization (FISH) assays reveal the colocalization of YY1 puncta with both the FOXM1 gene locus and its nascent RNA transcript. Overall, this study demonstrates that YY1 activates target gene expression through forming liquid-liquid phase separation condensates to compartmentalize both coactivators and enhancer elements, and the histidine cluster of YY1 plays a determinant role in this regulatory mechanism.

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

Simple Summary

YY1 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.

Abstract

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.

Yin Yang 1 regulates ITGAV and ITGB1, contributing to improved prognosis of colorectal cancer

Yin Yang 1 (YY1) is a multifunctional transcription factor with critical roles in carcinogenesis and metastasis. However, its biological role and clinical impact in colorectal cancer (CRC) remain unclear. In the present study, the function and underlying molecular mechanisms of YY1 in CRC progression were investigated. The immunohistochemistry (IHC) of 143 CRC tissues revealed a significant correlation of low YY1 expression with aggressive clinicopathological features, increased metastasis and recurrence and poor patient survival. Multivariate analysis identified low YY1 expression as an independent poor prognostic factor. Subsequently, the IHC of 66 paired CRC primary tumor and liver metastasis tissues revealed that low YY1 expression in the primary CRC was significantly associated with multiple liver metastases, major hepatectomy, extrahepatic metastasis and poor prognosis. In vitro experiments revealed that YY1 knockdown promoted the migration and invasion of CRC cells. To examine the downstream genes of YY1, a cDNA microarray assay was conducted and the differentially expressed genes between the YY1‑knockdown and control cells were compared. Integrin alpha V (ITGAV) and integrin beta 1 (ITGB1) were identified as upregulated hub genes using gene enrichment analysis and protein‑protein interaction analyses. Western blotting and IHC confirmed YY1 expression to be negatively correlated with ITGAV and ITGB1 expression. In summary, it was revealed that YY1, as a tumor‑suppressor in CRC, contributes to the survival of patients with CRC. Low YY1 expression was associated with the poor prognosis of the patients with primary CRC and liver metastases. YY1 suppressed the expression of ITGAV and ITGB1, and this transcriptional regulation may lead to the suppression of CRC cell migration and invasion.

YY1 activates EMI2 and promotes the progression of cholangiocarcinoma through the PI3K/Akt signaling axis

BACKGROUND

Cholangiocarcinoma (CCA) is one of the deadliest cancers of the digestive tract. The prognosis of CCA is poor and the 5-year survival rate is low. Bioinformatic analysis showed that early mitotic inhibitor 2 (EMI2) was overexpressed in CCA but the underlying mechanism is not known.

METHODS

The data on bile duct carcinoma from TCGA and GEO databases were used to detect the expression of EMI2. The transcription factors of EMI2 were predicted using JASPAR and PROMO databases. Among the predicted transcription factors, YY1 has been rarely reported in cholangiocarcinoma, and was verified using the luciferase reporter gene assay. RT-PCR was performed to predict the downstream pathway of EMI2, and PI3K/Akt was suspected to be associated with it. Subsequently, in vivo and in vitro experiments were conducted to verify the effects of silencing and overexpressing EMI2 and YY1 on the proliferation, invasion, and metastasis of the bile duct cancer cells.

RESULTS

EMI2 was highly expressed in CCA. Silencing EMI2 inhibited the proliferation, invasion, and migration of CCA cells, arrested cell cycle in the G1 phase, and promoted of apoptosis. The luciferase reporter gene assay showed that YY1 bound to the promoter region of EMI2, and after silencing YY1, the expression of EMI2 decreased and the progression of CCA was inhibited. Moreover, key proteins in the PI3K/Akt signaling pathway decreased after silencing EMI2.

CONCLUSION

EMI2 may be one of the direct targets of YY1 and promotes the progression of CCA through the PI3K/Akt signaling pathway.

The Protective Role of Yin-Yang 1 in Cardiac Injury and Remodeling After Myocardial Infarction

Background Exploring potential therapeutic target is of great significance for myocardial infarction (MI) and post-MI heart failure. Transcription factor Yin-Yang 1 (YY1) is an essential regulator of apoptosis and angiogenesis, but its role in MI is unclear. Methods and Results The expression of YY1 was assessed in the C57BL/6J mouse heart following MI. Overexpression or silencing of YY1 in the mouse heart was achieved by adeno-associated virus 9 injection. The survival, cardiac function, and scar size, as well as the apoptosis, angiogenesis, cardiac fibrosis, T helper 2 lymphocyte cytokine production, and macrophage polarization were assessed. The effects of YY1 on Akt phosphorylation and vascular endothelial growth factor production were also investigated. The expression of YY1 in heart was significantly stimulated by MI. The survival rate, cardiac function, scar size, and left ventricular volume of mice were improved by YY1 overexpression but worsened by YY1 silencing. YY1 alleviated cardiac apoptosis and fibrosis, promoted angiogenesis, T helper 2 cytokine production, and M2 macrophage polarization in the post-MI heart, it also enhanced the tube formation and migration ability of endothelial cells. Enhanced Akt phosphorylation, along with the increased vascular endothelial growth factor levels were observed in presence of YY1 overexpression. Conclusions YY1 ameliorates cardiac injury and remodeling after MI by repressing cardiomyocyte apoptosis and boosting angiogenesis, which might be ascribed to the enhancement of Akt phosphorylation and the subsequent vascular endothelial growth factor up-regulation. Increased T helper 2 cytokine production and M2 macrophage polarization may also be involved in YY1's cardioprotective effects. These findings supported YY1 as a potential target for therapeutic investigation of MI.

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

Simple Summary

Both 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.

Abstract

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.

Biological roles of Yin Yang 2: Its implications in physiological and pathological events

Yin yang 2 (YY2) is a multifunctional zinc finger protein that belongs to the yin yang (YY) family. YY2 has dual function in regulating gene expression, as it could act either as a transcriptional activator or as a repressor of its target genes. YY2 could regulate genes that have been previously identified as targets of yin yang 1 (YY1), another member of the YY family, by binding to their common binding sequences. However, recent studies revealed that YY2 also has its own specific binding sequences, leading to its particular biological functions distinct from those of YY1. Furthermore, they have different levels or even opposite regulatory effects on common target genes, suggesting the importance of balanced YY1 and YY2 regulations in maintaining proper cellular homeostasis and biological functions. Recent studies revealed that YY2 plays crucial roles in maintaining stemness and regulating differentiation potential of embryonic stem cells, as well as in the development of the brain, nervous and cardiovascular systems. YY2 expression is also closely related to diseases, as it could act as a tumour suppressor gene that regulates tumour cell proliferation and metastasis. Moreover, YY2 is also involved in immune regulation and immune surveillance. Herein, we summarize recent perspectives regarding the regulatory functions of YY2, as well as its biological functions and relation with diseases.

Transcriptional Factor Yin Yang 1 Promotes the Stemness of Breast Cancer Cells by Suppressing miR-873-5p Transcriptional Activity

Transcription factor Yin Yang 1 (YY1) is upregulated in multiple tumors and plays essential roles in tumor proliferation and metastasis. However, the function of YY1 in breast cancer stemness remains unclear. Herein, we found that YY1 expression was negatively correlated with the overall survival and relapse-free survival of breast cancer patients and positively correlated with the expression of stemness markers in breast cancer. Overexpression of YY1 increased the expression of stemness markers, elevated CD44+CD24- cell sub-population, and enhanced the capacity of cell spheroid formation and tumor-initiation. In contrast, YY1 knockdown exhibited the opposite effects. Mechanistically, YY1 decreased microRNA-873-5p (miR-873-5p) level by recruiting histone deacetylase 4 (HDAC4) and HDAC9 to miR-873-5p promoter and thus increasing the deacetylation level of miR-873-5p promoter. Sequentially, YY1 activated the downstream PI3K/AKT and ERK1/2 pathways, which have been confirmed to be suppressed by miR-873-5p in our recent work. Moreover, the suppressed effect of YY1/miR-873-5p axis on the stemness of breast cancer cells was partially dependent on PI3K/AKT and ERK1/2 pathways. Finally, it was found that the YY1/miR-873-5p axis is involved in the chemoresistance of breast cancer cells. Our study defines a novel YY1/miR-873-5p axis responsible for the stemness of breast cancer cells.

Characterization of YY1 OPB Peptide for its Anticancer Activity

BACKGROUND

The oncoprotein binding (OPB) domain of Yin Yang 1 (YY1) consists of 26 amino acids between G201 and S226, and is involved in YY1 interaction with multiple oncogene products, including MDM2, AKT, EZH2 and E1A. Through the OPB domain, YY1 promotes the oncogenic or proliferative regulation of these oncoproteins in cancer cells. We previously demonstrated that a peptide with the OPB sequence blocked YY1-AKT interaction and inhibited breast cancer cell proliferation.

OBJECTIVE

In the current study, we characterized the OPB domain and determined a minimal region for peptide design to suppress cancer cells.

METHODS

Using alanine-scan method, we identified that the amino acids at OPB C-terminal are essential to YY1 binding to AKT. Further studies suggested that serine and threonine residues, but not lysines, in OPB play a key role in YY1-AKT interaction. We generated GFP fusion expression vectors to express OPB peptides with serially deleted N-terminal and found that OPB1 (i.e. G201-S226) is cytoplasmic, but OPB2 (i.e. E206-S226), OPB3 (i.e. E206-S226) and control peptide were both nuclear and cytoplasmic.

RESULTS

Both OPB1 and 2 inhibited breast cancer cell proliferation and migration, but OPB3 exhibited similar effects to control. OPB1 and 2 caused cell cycle arrest at G1 phase, increased p53 and p21 expression, and reduced AKT(S473) phosphorylation in MCF-7 cells, but not in MDA-MB-231 cells.

CONCLUSION

Overall, the serines and threonines of OPB are essential to YY1 binding to oncoproteins, and OPB peptide can be minimized to E206-S226 that maintain inhibitory activity to YY1- promoted cell proliferation.

Nectandrin B-mediated activation of the AMPK pathway prevents cellular senescence in human diploid fibroblasts by reducing intracellular ROS levels

Nectandrin B (NecB) is a bioactive lignan compound isolated from Myristica fragrans (nutmeg), which functions as an activator of AMP-activated protein kinase (AMPK). Because we recently found that treatment with NecB increased the cell viability of old human diploid fibroblasts (HDFs), the underlying molecular mechanism was investigated. NecB treatment in old HDFs reduced the activity staining of senescence-associated β-galactosidase and the levels of senescence markers, such as the Ser¹⁵ phosphorylated p53, caveolin-1, p21^waf1, p16^ink4a, p27^kip1, and cyclin D1. NecB treatment increased that in S phase, indicating a enhancement of cell cycle entry. Interestingly, NecB treatment ameliorated age-dependent activation of AMPK in old HDFs. Moreover, NecB reversed the age-dependent expression and/or activity changes of certain sirtuins (SIRT1-5), and cell survival/death-related proteins. The transcriptional activity of Yin-Yang 1 and the expression of downstream proteins were elevated in NecB-treated old HDFs. In addition, NecB treatment exerted a radical scavenging effect in vitro, reduced cellular ROS levels, and increased antioxidant enzymes in old HDFs. Moreover, NecB-mediated activation of the AMPK pathway reduced intracellular ROS levels. These results suggest that NecB-induced protection against cellular senescence is mediated by ROS-scavenging through activation of AMPK. NecB might be useful in ameliorating age-related diseases and extending human lifespan.

Transcriptional factor Yin Yang 1 facilitates the stemness of ovarian cancer via suppressing miR-99a activity through enhancing its deacetylation level

The promoting effects of transcriptional factor Yin Yang 1 (YY1) have been confirmed in various tumors, however, its roles in ovarian cancer (OC) progression are still unclear. Here, Kaplan-Meier Plotter analysis was used to determine the correlation between YY1 expression and the survival of OC patients. It was found that YY1 expression was negatively correlated with the overall survival, progression-free survival and post-progression survival of OC patients. Functional experiments indicated that overexpression of YY1 facilitated the stemness of OC cells, while YY1 knockdown reduced it. MiRNAs-based RNA-sequencing analysis showed that miR-99a was the mostly upregulated miRNA in RNA extracted from OC cells with YY1 knockdown. Mechanistic studies revealed that YY1 recruited (Histone deacetylase) HDAC5 to the promoter of miR-99a, and subsequently enhanced miR-99a deacetylation level and decreased miR-99a level. Additionally, overexpression of miR-99a or knockdown of HDAC5 attenuated the promoting effects of YY1 on the stemness of OC cells. This work firstly indicated a novel YY1/miR-99a axis, which promotes the stemness of OC cells.

The biological implications of Yin Yang 1 in the hallmarks of cancer

Tumorigenesis is a multistep process characterized by the acquisition of genetic and epigenetic alterations. During the course of malignancy development, tumor cells acquire several features that allow them to survive and adapt to the stress-related conditions of the tumor microenvironment. These properties, which are known as hallmarks of cancer, include uncontrolled cell proliferation, metabolic reprogramming, tumor angiogenesis, metastasis, and immune system evasion. Zinc-finger protein Yin Yang 1 (YY1) regulates numerous genes involved in cell death, cell cycle, cellular metabolism, and inflammatory response. YY1 is highly expressed in many cancers, whereby it is associated with cell proliferation, survival, and metabolic reprogramming. Furthermore, recent studies also have demonstrated the important role of YY1-related non-coding RNAs in acquiring cancer-specific characteristics. Therefore, these YY1-related non-coding RNAs are also crucial for YY1-mediated tumorigenesis. Herein, we summarize recent progress with respect to YY1 and its biological implications in the context of hallmarks of cancer.

miR-410-3p regulates proliferation and apoptosis of fibroblast-like synoviocytes by targeting YY1 in rheumatoid arthritis

In our previous study, miR-410-3p had been confirmed to regulate inflammatory cytokine release in rheumatoid arthritis fibroblast-like synoviocytes (RA FLSs). However, other biological functions of miR-410-3p in RA FLSs still remain unexplored. In the present study, we focused on the effect of miR-410-3p on proliferation, apoptosis, and cell cycle of RA FLSs, and explored the potential underlying mechanism. miR-410-3p mRNA levels in the synovium and FLSs of patients with RA and of healthy controls were quantitated by RT-qPCR. The levels of miR-410-3p were reduced in both synovium and FLSs from patients with RA. Next, we focused on the roles of miR-410-3p in cell viability, apoptosis, and cell cycle, by transfecting miR-410-3p mimics and inhibitor into RA FLSs, and conducting CCK-8 assay, EdU staining and flow cytometry. Results showed that miR-410-3p up-regulation suppressed proliferation, promoted apoptosis and G1-S phase transition while miR-410-3p down-regulation had opposite effects. YY1 was verified as a direct target gene of miR-410-3p through the luciferase reporter system; YY1 up-regulation was able to rescue the effects of miR-410-3p in RA FLSs. Taken together, our current findings might provide a potential therapeutic target for RA.

Functional analysis of YY1 zinc fingers through cysteine mutagenesis

As a transcription factor, Yin Yang 1 (YY1) either activates or represses gene expression depending on its recruited cofactors. The YY1 C-terminal consists of four zinc fingers (ZF) that are responsible for its DNA binding. However, the contribution of each YY1 ZF to its functions have not been fully elucidated. In this study, we used alanines to replace YY1 cysteines that are crucial to ZFs in binding to DNA. We characterized these YY1 mutants for their DNA binding, transcriptional activity, and functional role in maintaining MDA-MB-231 cell proliferation. We demonstrated that ZFs 2 and 3 are essential to the general biological activity of YY1. ZF 1 showed relatively low importance, while ZF 4 is virtually dispensable for YY1 function.

YY1 regulates cancer cell immune resistance by modulating PD-L1 expression

Recent advances in the treatment of various cancers have resulted in the adaptation of several novel immunotherapeutic strategies. Notably, the recent intervention through immune checkpoint inhibitors has resulted in significant clinical responses and prolongation of survival in patients with several therapy-resistant cancers (melanoma, lung, bladder, etc.). This intervention was mediated by various antibodies directed against inhibitory receptors expressed on cytotoxic T-cells or against corresponding ligands expressed on tumor cells and other cells in the tumor microenvironment (TME). However, the clinical responses were only observed in a subset of the treated patients; it was not clear why the remaining patients did not respond to checkpoint inhibitor therapies. One hypothesis stated that the levels of PD-L1 expression correlated with poor clinical responses to cell-mediated anti-tumor immunotherapy. Hence, exploring the underlying mechanisms that regulate PD-L1 expression on tumor cells is one approach to target such mechanisms to reduce PD-L1 expression and, therefore, sensitize the resistant tumor cells to respond to PD-1/PD-L1 antibody treatments. Various investigations revealed that the overexpression of the transcription factor Yin Yang 1 (YY1) in most cancers is involved in the regulation of tumor cells' resistance to cell-mediated immunotherapies. We, therefore, hypothesized that the role of YY1 in cancer immune resistance may be correlated with PD-L1 overexpression on cancer cells. This hypothesis was investigated and analysis of the reported literature revealed that several signaling crosstalk pathways exist between the regulations of both YY1 and PD-L1 expressions. Such pathways include p53, miR34a, STAT3, NF-kB, PI3K/AKT/mTOR, c-Myc, and COX-2. Noteworthy, many clinical and pre-clinical drugs have been utilized to target these above pathways in various cancers independent of their roles in the regulation of PD-L1 expression. Therefore, the direct inhibition of YY1 and/or the use of the above targeted drugs in combination with checkpoint inhibitors should result in enhancing the cell-mediated anti-tumor cell response and also reverse the resistance observed with the use of checkpoint inhibitors alone.

Targeting mTOR in Acute Lymphoblastic Leukemia

Acute Lymphoblastic Leukemia (ALL) is an aggressive hematologic disorder and constitutes approximately 25% of cancer diagnoses among children and teenagers. Pediatric patients have a favourable prognosis, with 5-years overall survival rates near 90%, while adult ALL still correlates with poorer survival. However, during the past few decades, the therapeutic outcome of adult ALL was significantly ameliorated, mainly due to intensive pediatric-based protocols of chemotherapy. Mammalian (or mechanistic) target of rapamycin (mTOR) is a conserved serine/threonine kinase belonging to the phosphatidylinositol 3-kinase (PI3K)-related kinase family (PIKK) and resides in two distinct signalling complexes named mTORC1, involved in mRNA translation and protein synthesis and mTORC2 that controls cell survival and migration. Moreover, both complexes are remarkably involved in metabolism regulation. Growing evidence reports that mTOR dysregulation is related to metastatic potential, cell proliferation and angiogenesis and given that PI3K/Akt/mTOR network activation is often associated with poor prognosis and chemoresistance in ALL, there is a constant need to discover novel inhibitors for ALL treatment. Here, the current knowledge of mTOR signalling and the development of anti-mTOR compounds are documented, reporting the most relevant results from both preclinical and clinical studies in ALL that have contributed significantly into their efficacy or failure.

MiR-141-3p Suppresses Tumor Growth and Metastasis in Papillary Thyroid Cancer via Targeting Yin Yang 1

MicroR-141-3p has been found to be downregulated in papillary thyroid carcinoma (PTC), while little is known about the cellular functions and precise signals elicited by miR-141-3p in PTC. The results of this study indicated that the expression of miR-141-3p was aberrantly down-regulated in PTC tissues and cell lines, compared with the adjacent normal tissues and normal thyroid epithelial cells. Furthermore, the miR-141-3p expression level was negatively associated with TNM stage and lymph node metastasis in PTC. Expression of miR-141-3p effectively inhibited cell growth, promoted apoptosis, and suppressed invasion in PTC cells. Meanwhile, miR-141-3p knockdown with miR-141-3p inhibitor reversed these effects. Consistent with the in vitro study, miR-141-3p also exhibited anti-neoplastic activity in vivo. Moreover, the results revealed that miR-141-3p directly recognized the 3' untranslated region (3'UTR) of Yin Yang 1 (YY1) and negatively regulated the expression of YY1 at both protein and mRNA levels. Ectopic expression of YY1 could effectively abrogate the anti-metastatic and proapoptotic effects of miR-141-3p. In summary, the findings suggested that miR-141-3p can act as a tumor suppressor in PTC and may be a potential therapeutic target for PTC treatment. Anat Rec, 302:258-268, 2019. © 2018 Wiley Periodicals, Inc.

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.

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.

Prognostic significance of high YY1AP1 and PCNA expression in colon adenocarcinoma

To investigate the relationship between YY1AP1 and various clinicopathological features of colon adenocarcinoma (COAD), we conducted immunohistochemical (IHC) analyses of human tissue microarrays. We found that YY1AP1 protein expression was significantly higher in tumor tissue of the colon and liver, and was significantly lower in tumor tissue of the kidney. An analysis that employed the SurvExpress database indicated that increased expression of YY1AP1 mRNA was significantly associated with the overall survival of COAD patients. To clarify the validity of YY1AP1 or PCNA as determined by the IHC analysis was performed on 59 paired samples from COAD and adjacent normal tissue. Statistically significant differences of immunoreactivity for YY1AP1 or PCNA protein expression was observed between COAD tissue and adjacent normal tissue. High protein expression levels of YY1AP1 and PCNA were also found to be significantly correlated with M-class and distant metastasis. We also determined that YY1AP1 was correlated with PCNA expression in COAD samples, and Kaplan-Meier survival curves indicated that YY1AP1 protein expression was significantly associated with poor survival. Finally, a univariate analysis demonstrated that YY1AP1 protein expression was related to YY1AP1 score, and multivariate analysis revealed that the YY1AP1 protein expression level was an independent risk factor of overall COAD survival. Taken together, our findings indicate that YY1AP1 expression plays an important role in the tumorigenesis and progression of COAD and could serve as a clinical prognostic indicator for COAD.

Inverse correlation between the metastasis suppressor RKIP and the metastasis inducer YY1: Contrasting roles in the regulation of chemo/immuno-resistance in cancer

Several gene products have been postulated to mediate inherent and/or acquired anticancer drug resistance and tumor metastasis. Among these, the metastasis suppressor and chemo-immuno-sensitizing gene product, Raf Kinase Inhibitor Protein (RKIP), is poorly expressed in many cancers. In contrast, the metastasis inducer and chemo-immuno-resistant factor Yin Yang 1 (YY1) is overexpressed in many cancers. This inverse relationship between RKIP and YY1 expression suggests that these two gene products may be regulated via cross-talks of molecular signaling pathways, culminating in the expression of different phenotypes based on their targets. Analyses of the molecular regulation of the expression patterns of RKIP and YY1 as well as epigenetic, post-transcriptional, and post-translational regulation revealed the existence of several effector mechanisms and crosstalk pathways, of which five pathways of relevance have been identified and analyzed. The five examined cross-talk pathways include the following loops: RKIP/NF-κB/Snail/YY1, p38/MAPK/RKIP/GSK3β/Snail/YY1, RKIP/Smurf2/YY1/Snail, RKIP/MAPK/Myc/Let-7/HMGA2/Snail/YY1, as well as RKIP/GPCR/STAT3/miR-34/YY1. Each loop is comprised of multiple interactions and cascades that provide evidence for YY1's negative regulation of RKIP expression and vice versa. These loops elucidate potential prognostic motifs and targets for therapeutic intervention. Chiefly, these findings suggest that targeted inhibition of YY1 by specific small molecule inhibitors and/or the specific induction of RKIP expression and activity are potential therapeutic strategies to block tumor growth and metastasis in many cancers, as well as to overcome anticancer drug resistance. These strategies present potential alternatives for their synergistic uses in combination with low doses of conventional chemo-immunotherapeutics and hence, increasing survival, reducing toxicity, and improving quality of life.