RUNX family members are covalently modified and regulated by PIAS1-mediated sumoylation

Runt-related transcription factors: from pathogenesis to therapeutic targets in multiple-organ fibrosis

Fibrosis is a partially manageable process that leads to scarring and tissue hardening by prompting myofibroblasts to deposit significant amounts of extracellular matrix (ECM) following injury. It results in detrimental consequences and pathological characteristics, which hinder the functioning of associated organs and increase mortality rates. Runt-related transcription factors (RUNX) are part of a highly conserved family of heterodimer transcription factors, comprising RUNX1, RUNX2, and RUNX3. They are involved in several biological processes and undergo various forms of post-translational modification. RUNX regulates multiple targets and pathways to impact fibrosis, indicating promise for clinical application. Therefore, its significance in the fibrosis process should not be disregarded. The review begins with an objective description of the structure, transcriptional mechanism, and biological function of RUNX1, RUNX2, and RUNX3. A subsequent analysis is made of their physiological relationship with heart, lung, kidney, and liver, followed by a focus on the signaling mechanism of RUNX in regulating fibrosis of these organs. Furthermore, potential agents or drugs targeting RUNX for treating organ fibrosis are summarized, along with an evaluation of the therapeutic prospects and potential value of RUNX in fibrosis. Further research into RUNX could contribute to the development of novel therapeutic approaches for fibrosis.

Endothelial RUNX3 controls LSEC dysfunction and angiocrine LRG1 signaling to prevent liver fibrosis

BACKGROUND AND AIMS

Liver fibrosis represents a global health burden, given the paucity of approved antifibrotic therapies. Liver sinusoidal endothelial cells (LSECs) play a major gatekeeping role in hepatic homeostasis and liver disease pathophysiology. In early tumorigenesis, runt-related transcription factor 3 (RUNX3) functions as a sentinel; however, its function in liver fibrosis in LSECs remains unclear. This study aimed to investigate the role of RUNX3 as an important regulator of the gatekeeping functions of LSECs and explore novel angiocrine regulators of liver fibrosis.

APPROACH AND RESULTS

Mice with endothelial Runx3 deficiency develop gradual and spontaneous liver fibrosis secondary to LSEC dysfunction, thereby more prone to liver injury. Mechanistic studies in human immortalized LSECs and mouse primary LSECs revealed that IL-6/JAK/STAT3 pathway activation was associated with LSEC dysfunction in the absence of RUNX3. Single-cell RNA sequencing and quantitative RT-PCR revealed that leucine-rich alpha-2-glycoprotein 1 ( LRG1 ) was highly expressed in RUNX3-deficient and dysfunctional LSECs. In in vitro and coculture experiments, RUNX3-depleted LSECs secreted LRG1, which activated HSCs throughTGFBR1-SMAD2/3 signaling in a paracrine manner. Furthermore, circulating LRG1 levels were elevated in mouse models of liver fibrosis and in patients with fatty liver and cirrhosis.

CONCLUSIONS

RUNX3 deficiency in the endothelium induces LSEC dysfunction, LRG1 secretion, and liver fibrosis progression. Therefore, endothelial RUNX3 is a crucial gatekeeping factor in LSECs, and profibrotic angiocrine LRG1 may be a novel target for combating liver fibrosis.

Rhythms in Remodeling: Posttranslational Regulation of Bone by the Circadian Clock

The circadian clock is a fundamental timekeeping system that regulates rhythmic biological processes in response to environmental light-dark cycles. In mammals, core clock genes (CLOCK, BMAL1, PER, and CRY) orchestrate these rhythms through transcriptional-translational feedback loops, influencing various physiological functions, including bone remodeling. Bone homeostasis relies on the coordinated activities of osteoblasts, osteoclasts, and osteocytes, with increasing evidence highlighting the role of circadian regulation in maintaining skeletal integrity. Disruptions in circadian rhythms are linked to bone disorders such as osteoporosis. Posttranslational modifications (PTMs), including phosphorylation, acetylation, and ubiquitination, serve as crucial regulators of both circadian mechanisms and bone metabolism. However, the specific role of PTMs in integrating circadian timing with bone remodeling remains underexplored. This review examines the intersection of circadian regulation and PTMs in bone biology, elucidating their impact on bone cell function and homeostasis. Understanding these interactions may uncover novel therapeutic targets for skeletal diseases associated with circadian disruptions.

RUNX3 inhibits KSHV lytic replication by binding to the viral genome and repressing transcription

Kaposi's sarcoma-associated herpesvirus (KSHV) belongs to the gamma herpesvirus family, which can cause human malignancies including Kaposi sarcoma, primary effusion lymphoma, and multicentric Castleman's diseases. KSHV typically maintains a persistent latent infection within the host. However, after exposure to intracellular or extracellular stimuli, KSHV lytic replication can be reactivated. The reactivation process of KSHV triggers the innate immune response to limit viral replication. Here, we found that the transcriptional regulator RUNX3 is transcriptionally upregulated by the NF-κB signaling pathway in KSHV-infected SLK cells and B cells during KSHV reactivation. Notably, knockdown of RUNX3 significantly promotes viral lytic replication as well as the gene transcription of KSHV. Consistent with this finding, overexpression of RUNX3 impairs viral lytic replication. Mechanistically, RUNX3 binds to the KSHV genome and limits viral replication through transcriptional repression, which is related to its DNA- and ATP-binding ability. However, KSHV has also evolved corresponding strategies to antagonize this inhibition by using the viral protein RTA to target RUNX3 for ubiquitination and proteasomal degradation. Altogether, our study suggests that RUNX3, a novel host-restriction factor of KSHV that represses the transcription of viral genes, may serve as a potential target to restrict KSHV transmission and disease development.IMPORTANCEThe reactivation of Kaposi's sarcoma-associated herpesvirus (KSHV) from latent infection to lytic replication is important for persistent viral infection and tumorigenicity. However, reactivation is a complex event, and the regulatory mechanisms of this process are not fully elucidated. Our study revealed that the host RUNX3 is upregulated by the NF-κB signaling pathway during KSHV reactivation, which can repress the transcription of KSHV genes. At the late stage of lytic replication, KSHV utilizes a mechanism involving RTA to degrade RUNX3, thus evading host inhibition. This finding helps elucidate the regulatory mechanism of the KSHV life cycle and may provide new clues for the development of therapeutic strategies for KSHV-associated diseases.

Aberrant SUMO2/3 modification of RUNX1 upon SENP1 inhibition is linked to the development of diabetic retinopathy in mice

Our previous report established that RUNX family transcription factor 1 (RUNX1) promotes proliferation of mouse retinal microvascular endothelial cells (mRMECs) and exacerbates diabetic retinopathy (DR). However, the mechanism behind the upregulation of RUNX1 remains unclear. This study aims to investigate the possible correlation between histone SUMOylation and RUNX1 in DR, as well as the involved molecules. A mouse model of diabetes was induced by streptozotocin (STZ). These mice had increased retinal thickness and elevated production of inflammatory cytokines. Additionally, they showed elevated levels of SUMO1 and SUMO2/3, but reduced levels of SUMO specific peptidase 1 (SENP1) in retinal tissues. Co-immunoprecipitation and Western blot assays revealed that the RUNX1 protein was primarily modified by SUMO2/3, and SENP1 inhibited SUMO2/3 modification, thereby reducing RUNX1 expression. Overexpression of SENP1 alleviated symptoms in mice and alleviated inflammation. In vitro experiments demonstrated that the SENP1 overexpression suppressed the proliferation, migration, and angiogenesis of high-glucose-induced mRMECs. However, further overexpression of RUNX1 counteracted the alleviating effects of SENP1 both in vivo and in vitro. In conclusion, this study demonstrates that the downregulation of SENP1 in DR leads to SUMO2/3-dependent activation of RUNX1. This activation promotes proliferation of mRMECs and exacerbates DR symptoms in mice.

PIAS1 impedes vascular endothelial injury and atherosclerotic plaque formation in diabetes by blocking the RUNX3/TSP-1 axis

The protein PIAS1 functions as a type of ubiquitin-protease, which is known to play an important regulatory role in various diseases, including cardiovascular diseases and cancers. Its mechanism of action primarily revolves around regulating the transcription, translation, and modification of target proteins. This study investigates role and mechanism of PIAS1 in the RUNX3/TSP-1 axis and confirms its therapeutic effects on diabetes-related complications in animal models. A diabetic vascular injury was induced in human umbilical vein endothelial cells (HUVECs) by stimulation with H2O2 and advanced glycation end product (AGE), and a streptozotocin (STZ)-induced mouse model of diabetes was constructed, followed by detection of endogenous PIAS1 expression and SUMOylation level of RUNX3. Effects of PIAS1 concerning RUNX3 and TSP-1 on the HUVEC apoptosis and inflammation were evaluated using the ectopic expression experiments. Down-regulated PIAS1 expression and SUMOylation level of RUNX3 were identified in the H2O2- and AGE-induced HUVEC model of diabetic vascular injury and STZ-induced mouse models of diabetes. PIAS1 promoted the SUMOylation of RUNX3 at the K148 site of RUNX3. PIAS1-mediated SUMOylation of RUNX3 reduced RUNX3 transactivation activity, weakened the binding of RUNX3 to the promoter region of TSP-1, and caused downregulation of TSP-1 expression. PIASI decreased the expression of TSP-1 by inhibiting H2O2- and AGE-induced RUNX3 de-SUMOylation, thereby arresting the inflammatory response and apoptosis of HUVECs. Besides, PIAS1 reduced vascular endothelial injury and atherosclerotic plaque formation in mouse models of diabetes by inhibiting the RUNX3/TSP-1 axis. Our study proved that PIAS1 suppressed vascular endothelial injury and atherosclerotic plaque formation in mouse models of diabetes via the RUNX3/TSP-1 axis.

RUNX3 Meets the Ubiquitin-Proteasome System in Cancer

RUNX3 is a transcription factor with regulatory roles in cell proliferation and development. While largely characterized as a tumor suppressor, RUNX3 can also be oncogenic in certain cancers. Many factors account for the tumor suppressor function of RUNX3, which is reflected by its ability to suppress cancer cell proliferation after expression-restoration, and its inactivation in cancer cells. Ubiquitination and proteasomal degradation represent a major mechanism for the inactivation of RUNX3 and the suppression of cancer cell proliferation. On the one hand, RUNX3 has been shown to facilitate the ubiquitination and proteasomal degradation of oncogenic proteins. On the other hand, RUNX3 can be inactivated through the ubiquitin-proteasome system. This review encapsulates two facets of RUNX3 in cancer: how RUNX3 suppresses cell proliferation by facilitating the ubiquitination and proteasomal degradation of oncogenic proteins, and how RUNX3 is degraded itself through interacting RNA-, protein-, and pathogen-mediated ubiquitination and proteasomal degradation.

The roles of Runx1 in skeletal development and osteoarthritis: A concise review

Runt-related transcription factor-1 (Runx1) is well known for its functions in hematopoiesis and leukemia but recent research has focused on its role in skeletal development and osteoarthritis (OA). Deficiency of the Runx1 gene is fatal in early embryonic development, and specific knockout of Runx1 in cell lineages of cartilage and bone leads to delayed cartilage formation and impaired bone calcification. Runx1 can regulate genes including collagen type II (Col2a1) and X (Col10a1), SRY-box transcription factor 9 (Sox9), aggrecan (Acan) and matrix metalloproteinase 13 (MMP-13), and the up-regulation of Runx1 improves the homeostasis of the whole joint, even in the pathological state. Moreover, Runx1 is activated as a response to mechanical compression, but impaired in the joint with the pathological progress associated with osteoarthritis. Therefore, interpretation about the role of Runx1 could enlarge our understanding of key marker genes in the skeletal development and an increased understanding of Runx1 could be helpful to identify treatments for osteoarthritis. This review provides the most up-to-date advances in the roles and bio-mechanisms of Runx1 in healthy joints and osteoarthritis from all currently published articles and gives novel insights in therapeutic approaches to OA based on Runx1.

SUMOylation in Skeletal Development, Homeostasis, and Disease

The modification of proteins by small ubiquitin-related modifier (SUMO) molecules, SUMOylation, is a key post-translational modification involved in a variety of biological processes, such as chromosome organization, DNA replication and repair, transcription, nuclear transport, and cell signaling transduction. In recent years, emerging evidence has shown that SUMOylation regulates the development and homeostasis of the skeletal system, with its dysregulation causing skeletal diseases, suggesting that SUMOylation pathways may serve as a promising therapeutic target. In this review, we summarize the current understanding of the molecular mechanisms by which SUMOylation pathways regulate skeletal cells in physiological and disease contexts.

Cancer-Associated Dysregulation of Sumo Regulators: Proteases and Ligases

SUMOylation is a post-translational modification that has emerged in recent decades as a mechanism involved in controlling diverse physiological processes and that is essential in vertebrates. The SUMO pathway is regulated by several enzymes, proteases and ligases being the main actors involved in the control of sumoylation of specific targets. Dysregulation of the expression, localization and function of these enzymes produces physiological changes that can lead to the appearance of different types of cancer, depending on the enzymes and target proteins involved. Among the most studied proteases and ligases, those of the SENP and PIAS families stand out, respectively. While the proteases involved in this pathway have specific SUMO activity, the ligases may have additional functions unrelated to sumoylation, which makes it more difficult to study their SUMO-associated role in cancer process. In this review we update the knowledge and advances in relation to the impact of dysregulation of SUMO proteases and ligases in cancer initiation and progression.

Hepatoprotective effects of sevoflurane against hepatic ischemia-reperfusion injury by regulating microRNA-124-3p-mediated TRAF3/CREB axis

The purpose of the present study is to define the role of sevoflurane (SEV) in hepatic ischemia-reperfusion (I/R) injury as well as its underlying mechanism. Initially, hepatic I/R animal models and I/R hepatocyte models were established in C57BL/6 mice and normal mouse hepatocytes (BNL CL.2) after SEV preconditioning, respectively, followed by detection of microRNA-124-3p (miR-124-3p), TRAF3, and CREB expression by RT-qPCR and Western blot analysis. In addition, miR-124-3p, TRAF3 and CREB expression in hepatocytes was altered to identify their roles in modulating the levels of glutathione transferase (GST), aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and inflammation-related factors and hepatocyte apoptosis by ELISA and flow cytometry respectively. The effects of SEV on the miR-124-3p/TRAF3/CREB axis were also verified in vitro and in vivo. IP assay was performed to verify the effect of TRAF3 on CREB ubiquitination in BNL CL.2 cells, and the cycloheximide (CHX) intervention experiment to detect the stability of CREB protein. SEV augmented the miR-124-3p expression in I/R animal and cell models. Moreover, SEV was observed to suppress I/R-induced liver damage, GST, ALT, and AST levels, hepatocyte apoptosis and inflammation. Overexpression of miR-124-3p resulted in alleviation of hepatic I/R injury, which was countered by TRAF3 overexpression. miR-124-3p targeted TRAF3, while TRAF3 promoted CREB ubiquitination and reduced protein stability of CREB. SEV could impede I/R-induced liver damage, GST, ALT, and AST levels, hepatocyte apoptosis and inflammation via mediation of the miR-124-3p/TRAF3/CREB axis in vitro and in vivo. Collectively, SEV may upregulate miR-124-3p to inhibit TRAF3 expression, thereby reducing the ubiquitination and degradation of CREB, alleviating hepatic I/R injury.

Oncogenic E3 ubiquitin ligase NEDD4 binds to KLF8 and regulates the microRNA-132/NRF2 axis in bladder cancer

The neuronally expressed developmentally downregulated 4 (NEDD4) gene encodes a ubiquitin ligase that targets the epithelial sodium channel for degradation and has been implicated in tumor growth in various cancers. Hence, in this study, we intended to characterize the functional relevance of the NEDD4-mediated Kruppel-like factor 8/microRNA-132/nuclear factor E2-related factor 2 (KLF8/miR-132/NRF2) axis in the development of bladder cancer. NEDD4 and KLF8 were overexpressed in bladder cancer tissues and were associated with poorer patient survival rates. In bladder cancer cells, NEDD4 intensified the stability and transcriptional activity of KLF8 through ubiquitination to augment cell viability and migratory ability. Our investigations revealed that NEDD4 promotes the binding of KLF8 to the miR-132 promoter region and inhibits the expression of miR-132. KLF8 inhibited the expression of miR-132 to augment the viability and migratory ability of bladder cancer cells. Furthermore, miR-132 downregulated the expression of NRF2 to restrict the viability and migratory ability of bladder cancer cells. In addition, in vivo findings verified that NEDD4 regulates the KLF8/miR-132/NRF2 axis by accelerating tumor growth and lung metastasis. In conclusion, this study highlights NEDD4 as a potential therapeutic target against tumor recurrence and metastasis in bladder cancer.

Expression patterns and prognostic value of RUNX genes in kidney cancer

Kidney cancer is the third most common malignancy of the urinary system, of which, kidney renal clear cell carcinoma (KIRC) accounts for the vast majority. Runt-related transcription factors (RUNX) are involved in multiple cellular functions. However, the diverse expression patterns and prognostic values of RUNX genes in kidney cancer remained to be elucidated. In our study, we mined the DNA methylation, transcriptional and survival data of RUNX genes in patients with different kinds of kidney cancer through Oncomine, Gene Expression Profiling Interactive Analysis, UALCAN, Kaplan–Meier Plotter, cBioPortal and LinkedOmics. We found that RUNX1 and RUNX3 were upregulated in KIRC tissues compared with those in normal tissues. The survival analysis results indicated a high transcription level of RUNX1 was associated with poor overall survival (OS) in KIRC patients. Furthermore, KIRC tumor tissues had significantly lower levels of RUNX1 promoter methylation than that in paracancerous tissues, with decreased DNA methylation of RUNX1 notably associated with poor OS in KIRC. In conclusion, our results revealed that RUNX1 may be a potential therapeutic target for treating KIRC, and RUNX1 promoter methylation level shows promise as a novel diagnostic and prognostic biomarker, which laid a foundation for further study.

Multifaceted HIV-1 Vif interactions with human E3 ubiquitin ligase and APOBEC3s

APOBEC3 (A3) proteins are a family of host antiviral restriction factors that potently inhibit various retroviral infections, including human immunodeficiency virus (HIV)-1. To overcome this restriction, HIV-1 virion infectivity factor (Vif) recruits the cellular cofactor CBFβ to assist in targeting A3 proteins to a host E3 ligase complex for polyubiquitination and subsequent proteasomal degradation. Intervention of the Vif-A3 interactions could be a promising therapeutic strategy to facilitate A3-mediated suppression of HIV-1 in patients. In this structural snapshot, we review the structural features of the recently determined structure of human A3F in complex with HIV-1 Vif and its cofactor CBFβ, discuss insights into the molecular principles of Vif-A3 interplay during the arms race between the virus and host, and highlight the therapeutic implications.

Restoring RUNX1 deficiency in RUNX1 familial platelet disorder by inhibiting its degradation

RUNX1 familial platelet disorder (RUNX1-FPD) is an autosomal dominant disorder caused by a monoallelic mutation of RUNX1, initially resulting in approximately half-normal RUNX1 activity. Clinical features include thrombocytopenia, platelet functional defects, and a predisposition to leukemia. RUNX1 is rapidly degraded through the ubiquitin-proteasome pathway. Moreover, it may autoregulate its expression. A predicted kinetic property of autoregulatory circuits is that transient perturbations of steady-state levels result in continued maintenance of expression at adjusted levels, even after inhibitors of degradation or inducers of transcription are withdrawn, suggesting that transient inhibition of RUNX1 degradation may have prolonged effects. We hypothesized that pharmacological inhibition of RUNX1 protein degradation could normalize RUNX1 protein levels, restore the number of platelets and their function, and potentially delay or prevent malignant transformation. In this study, we evaluated cell lines, induced pluripotent stem cells derived from patients with RUNX1-FPD, RUNX1-FPD primary bone marrow cells, and acute myeloid leukemia blood cells from patients with RUNX1 mutations. The results showed that, in some circumstances, transient expression of exogenous RUNX1 or inhibition of steps leading to RUNX1 ubiquitylation and proteasomal degradation restored RUNX1 levels, thereby advancing megakaryocytic differentiation in vitro. Thus, drugs retarding RUNX1 proteolytic degradation may represent a therapeutic avenue for treating bleeding complications and preventing leukemia in RUNX1-FPD.

RUNX3 methylation drives hypoxia-induced cell proliferation and antiapoptosis in early tumorigenesis

Inactivation of tumor suppressor Runt-related transcription factor 3 (RUNX3) plays an important role during early tumorigenesis. However, posttranslational modifications (PTM)-based mechanism for the inactivation of RUNX3 under hypoxia is still not fully understood. Here, we demonstrate a mechanism that G9a, lysine-specific methyltransferase (KMT), modulates RUNX3 through PTM under hypoxia. Hypoxia significantly increased G9a protein level and G9a interacted with RUNX3 Runt domain, which led to increased methylation of RUNX3 at K129 and K171. This methylation inactivated transactivation activity of RUNX3 by reducing interactions with CBFβ and p300 cofactors, as well as reducing acetylation of RUNX3 by p300, which is involved in nucleocytoplasmic transport by importin-α1. G9a-mediated methylation of RUNX3 under hypoxia promotes cancer cell proliferation by increasing cell cycle or cell division, while suppresses immune response and apoptosis, thereby promoting tumor growth during early tumorigenesis. Our results demonstrate the molecular mechanism of RUNX3 inactivation by G9a-mediated methylation for cell proliferation and antiapoptosis under hypoxia, which can be a therapeutic or preventive target to control tumor growth during early tumorigenesis.

The Roles of RUNX Family Proteins in Development of Immune Cells

The Runt-related transcription factors (RUNX) transcription factors have been known for their critical roles in numerous developmental processes and diseases such as autoimmune disorders and cancer. Especially, RUNX proteins are best known for their roles in hematopoiesis, particularly during the development of T cells. As scientists discover more types of new immune cells, the functional diversity of RUNX proteins also has been increased over time. Furthermore, recent research has revealed complicated transcriptional networks involving RUNX proteins by the current technical advances. Databases established by next generation sequencing data analysis has identified ever increasing numbers of potential targets for RUNX proteins and other transcription factors. Here, we summarize diverse functions of RUNX proteins mainly on lymphoid lineage cells by incorporating recent discoveries.

RUNX transcription factors: orchestrators of development

RUNX transcription factors orchestrate many different aspects of biology, including basic cellular and developmental processes, stem cell biology and tumorigenesis. In this Primer, we introduce the molecular hallmarks of the three mammalian RUNX genes, RUNX1, RUNX2 and RUNX3, and discuss the regulation of their activities and their mechanisms of action. We then review their crucial roles in the specification and maintenance of a wide array of tissues during embryonic development and adult homeostasis.

Expression analysis of protein inhibitor of activated STAT (PIAS) genes in IFNβ-treated multiple sclerosis patients

Objectives

Protein inhibitors of activated STAT (PIAS) are transcription co-regulator of the Janus kinase/signal transducer and activator of transcription signaling pathway as well as nuclear factor-κB family of transcription factors. Both of them are involved in cytokine release during inflammatory response.

Patients and methods

Considering the role of cytokine imbalance in the pathogenesis of multiple sclerosis (MS), we compared blood expressions of PIAS1-4 genes in 48 interferon β (IFNβ)-treated MS patients with those of healthy subjects by means of real time PCR.

Results

Although the expression levels of these genes were not significantly different between MS patients and healthy subjects, significant inverse correlations have been found between PIAS1 expression and age at disease onset. PIAS2 and PIAS3 expressions were inversely correlated with Expanded Disability Status Scale (EDSS) in patients. Moreover, PIAS3 expression was correlated with disease duration in patients and with age in controls. In addition, PIAS4 expression was inversely correlated with EDSS and age at disease onset while it was positively correlated with disease duration.

Conclusion

The present study provides evidences for altered expression of PIAS genes in IFNβ-treated MS patients compared with healthy subjects. However, future studies are needed for elaboration of their exact function in this disorder.

Molecular and functional evaluation of a novel HIF inhibitor, benzopyranyl 1,2,3-triazole compound

Hypoxia occurs in a variety of pathological events, including the formation of solid tumors. Hypoxia-inducible factor (HIF)-1α is stabilized under hypoxic conditions and is a key molecule in tumor growth and angiogenesis. Seeking to develop novel cancer therapeutics, we investigated small molecules from our in-house chemical libraries to target HIF-1α. We employed a dual-luciferase assay that uses a luciferase (Luc) reporter vector harboring five copies of hypoxia-responsive element (HRE) in the promoter. Under hypoxic conditions that increased Luc reporter activity by four-fold, we screened 144 different compounds, nine of which showed 30–50% inhibition of hypoxia-induced Luc reporter activity. Among these, “Compound 12, a benzopyranyl 1,2,3-triazole” was the most efficient at inhibiting the expression of HIF-1α under hypoxic conditions, reducing its expression by 80%. Under hypoxic conditions, the half maximal IC₅₀ of the compound was 24 nM in HEK-293 human embryonic kidney cells, and 2 nM in A549 human lung carcinoma cells. Under hypoxic conditions, Compound 12 increased hydroxylated HIF-1α levels and HIF-1α ubiquitination, and also dose-dependently decreased HIF-1α target gene expression as well as vascular endothelial growth factor (VEGF) secretion. Furthermore, this compound inhibited VEGF-induced in vitro angiogenesis in human umbilical vein endothelial cells (HUVECs), and in vivo, it inhibited chick chorioallantoic membrane angiogenesis. In allogaft assays, cotreatment with Compound 12 and gefitinib significantly inhibited tumor growth and angiogenesis. Compound 12 can be a novel inhibitor of HIF-1α by accelerating its degradation, and shows much potential as an anti-cancer agent through its ability to suppress tumor growth and angiogenesis.

GATA4 Directly Regulates Runx2 Expression and Osteoblast Differentiation

GATA4 is a zinc‐finger transcription factor that is a pioneer factor in various tissues and regulates tissue‐specific gene regulation. In vivo deletion of Gata4 using Cre‐recombinase under the control of the Col1a1 2.3 kb promoter showed significantly reduced values for trabecular bone properties by microCT analysis of femur and tibia of 14‐week‐old male and female mice, suggesting GATA4 is necessary for maintaining normal adult bone phenotype. Quantitative PCR analysis revealed higher expression of Gata4 in trabecular bone compared with cortical bone, suggesting a role for GATA4 in maintaining normal trabecular bone mass. In vivo and in vitro, reduction of Gata4 correlates with reduced Runx2 gene expression, along with reduced osteoblast mineralization. To determine if Runx2 is a direct target of GATA4, chromatin immunoprecipitation (ChIP) was performed, and it demonstrated that GATA4 is recruited to the two Runx2 promoters and an enhancer region. Furthermore, when Gata4 is knocked down, the chromatin at the Runx2 region is not open, as detected by DNase assays and ChIP with antibodies to the open chromatin marks H3K4me2 (histone 3 lysine 4 dimethylation) and H3K27ac (histone 3 lysine 27 acetylation) and the closed chromatin mark H3K27me2 (histone 3 lysine 27 trimethylation). Together, the data suggest that GATA4 binds near the Runx2 promoter and enhancer and helps maintain open chromatin to regulate Runx2 expression leading to bone mineralization. © 2017 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Ablation of Adenosine Monophosphate-Activated Protein Kinase α1 in Vascular Smooth Muscle Cells Promotes Diet-Induced Atherosclerotic Calcification In Vivo

RATIONALE

Atherosclerotic calcification is highly linked with plaque rapture. How calcification is regulated is poorly characterized.

OBJECTIVE

We sought to determine the contributions of AMP-activated protein kinase (AMPK) in atherosclerotic calcification.

METHODS AND RESULTS

Aortic calcification was evaluated in aortic roots and brachiocephalic arteries of atherosclerotic prone ApoE(-/-) mice or in mice with dual deficiencies of ApoE and AMPKα isoforms in whole body (ApoE(-/-)/AMPKα1(-/-) and ApoE(-/-)/AMPKα2(-/-)) or vascular smooth muscle cell (VSMC)-specific or macrophage-specific knockout of AMPKα1 fed with Western diet for 24 weeks. Genetic deficiency of AMPKα1 but not of AMPKα2 promoted atherosclerotic calcification and the expression of Runx2 (Runt-related transcription factor). Conversely, chronic administration of metformin, which activated AMPK, markedly reduced atherosclerotic calcification and Runx2 expression in ApoE(-/-) mice but had less effects in ApoE(-/-)/AMPKα1(-/-) mice. Furthermore, VSMC-specific but not macrophage-specific ablation of AMPKα1 promoted aortic calcification in vivo. Ablation of AMPKα1 in VSMC prevented Runx2 from proteasome degradation in parallel with aberrant osteoblastic differentiation of VSMC, whereas AMPK activation promoted Runx2 post-translational modification by small ubiquitin-like modifier (SUMO, SUMOylation), which is associated with its instability. Mechanically, we found that AMPKα1 directly phosphorylated protein inhibitor of activated STAT-1 (PIAS1), the SUMO E3-ligase of Runx2, at serine 510, to promote its SUMO E3-ligase activity. Finally, mutation of protein inhibitor of activated STAT-1 at serine 510 suppressed metformin-induced Runx2 SUMOylation and subsequently prevented metformin's effect on reducing oxidized low-density lipoprotein-triggered Runx2 expression in VSMC.

CONCLUSIONS

AMPKα1 phosphorylated protein inhibitor of activated STAT-1 to promote Runx2 SUMOylation and subsequently lead to its instability. AMPKα1 deficiency in VSMC increased Runx2 expression and promoted atherosclerotic calcification in vivo.

A novel Lozenge gene in silkworm, Bombyx mori regulates the melanization response of hemolymph

Runt-related (RUNX) transcription factors are evolutionarily conserved either in vertebrate or invertebrate. Lozenge (Lz), a members of RUNX family as well as homologue of AML-1, functions as an important transcription factor regulating the hemocytes differentiation. In this paper, we identified and characterized RUNX family especially Lz in silkworm, which is a lepidopteran model insect. The gene expression analysis illustrated that BmLz was highly expressed in hemocytes throughout the whole development period, and reached a peak in glutonous stage. Over-expression of BmLz in silkworm accelerated the melanization process of hemolymph, and led to instantaneously up-regulation of prophenoloxidases (PPOs), which were key enzymes in the melanization process. Further down-regulation of BmLz expression by RNA interference resulted in the significant delay of melanization reaction of hemolymph. These findings suggested that BmLz regulated the melanization process of hemolymph by inducing PPOs expression, and played a critical role in innate immunity defense in silkworm.

Targeting the sumoylation pathway in cancer stem cells

Cancer stem cells (CSCs) represent a subset of tumor cells with tumor-initiating potential. We recently demonstrated that inhibition of the sumoylation pathway cleared the CSC population and repressed the outgrowth of basal breast cancer xenografts. Targeting the sumoylation pathway offers a novel treatment strategy for basal breast cancer.

Regulation of epithelial-mesenchymal transition through SUMOylation of transcription factors

Carcinoma cells can transition from an epithelial-to-mesenchymal differentiation state through a process known as epithelial-mesenchymal transition (EMT). The process of EMT is characterized by alterations in the pattern of gene expression and is associated with a loss of cell polarity, an increase in invasiveness, and an increase in cells expressing cancer stem cell (CSC) markers. The reverse process of mesenchymal-to-epithelial transition (MET) can also occur, though the transitions characterizing EMT and MET can be incomplete. A growing number of transcription factors have been identified that influence the EMT/MET processes. Interestingly, SUMOylation regulates the functional activity of many of the transcription factors governing transitions between epithelial and mesenchymal states. In some cases, the transcription factor is a small ubiquitin-like modifier conjugated directly, thus altering its transcriptional activity or cell trafficking. In other cases, SUMOylation alters transcriptional mechanisms through secondary effects. This review explores the role of SUMOylation in controlling transcriptional mechanisms that regulate EMT/MET in cancer. Developing new drugs that specifically target SUMOylation offers a novel therapeutic approach to block tumor growth and metastasis.