Expression profile of MTA1 in adult mouse tissues

β-Hydroxybutyrate alleviates brain aging through the MTA1 pathway in D-galactose injured mice

Aging is an inevitable law of the process of life during which many physiological functions change. Brain aging is an important mechanism in the occurrence and development of degenerative diseases of the central nervous system. β-Hydroxybutyrate (BHBA) is a water-soluble, endogenous small-molecule ketone that can cross the blood-brain barrier and induce neuroprotective effects. This study aimed to investigate the effects of BHBA on D-galactose (D-gal) induced aging in mice and its underlying mechanisms using in vitro and in vivo experiments. These results indicated that D-gal-induced senescence, oxidative stress, and inflammatory responses were inhibited by BHBA, and autophagy was promoted by BHBA. Mechanistically, we explored the role of metastasis-associated antigen-1 (MTA1) in D-gal-induced damaged in HT22 cells using small interfering RNA (siRNA). The results demonstrated that the expression of MTA1 was significantly increased by BHBA, which attenuated D-gal-induced aging, oxidative stress, and inflammatory responses, and promoted autophagy through the upregulation of MTA1. In conclusion, MTA1 may be a novel target for treating aging caused by neurological damage. BHBA improves brain aging by activating the MTA1 pathway.

Metastasis-associated 1 localizes to the sarcomeric Z-disc and is implicated in skeletal muscle pathology

Metastasis-associated 1 (MTA1), a subunit of the nucleosome remodeling and histone deacetylation (NuRD) corepressor complex, was reported to be expressed in the cytoplasm of skeletal muscles. However, the exact subcellular localization and the functional implications of MTA1 in skeletal muscles have not been examined. This study aims to demonstrate the subcellular localization of MTA1 in skeletal muscles and reveal its possible roles in skeletal muscle pathogenesis. Striated muscles (skeletal and cardiac) from C57BL/6 mice of 4-5 weeks were collected to examine the expression of MTA1 by Western blotting and immunohistochemistry. Immunofluorescence and immunoelectron microscopy were performed for MTA1, α-actinin (a Z-disc marker protein), and SMN (survival of motor neuron) proteins. Gene Expression Omnibus (GEO) data sets were analyzed using the GEO2R online tool to explore the functional implications of MTA1 in skeletal muscles. MTA1 expression was detected by Western blotting and immunohistochemistry in skeletal and cardiac muscles. Subcellular localization of MTA1 was found in the Z-disc of sarcomeres, where α-actinin and SMN were expressed. Data mining of GEO profiles suggested that MTA1 dysregulation is associated with multiple skeletal muscle defects, such as Duchenne muscular dystrophy, Emery-Dreifuss muscular dystrophy, nemaline myopathy, and dermatomyositis. The GEO analysis also showed that MTA1 expression gradually decreased with age in mouse skeletal muscle precursor cells. The subcellular localization of MTA1 in sarcomeres of skeletal muscles implies its biological roles in sarcomere structures and its possible contribution to skeletal muscle pathology.

Metastasis-associated protein 1 participates in regulating luminal acidification of the epididymis via repressing estrogen receptor alpha transcription

BACKGROUND

As a component of the nucleosome remodeling and deacetylating (NuRD) complex, metastasis-associated protein 1 (MTA1) has been reported to be abundant in male reproductive system and might participate in spermatogenesis and sperm maturation, whereas the precise functional role of MTA1 in these processes is still undetermined.

OBJECTIVE

To investigate the effect and potential function of MTA1 in male fertility.

MATERIALS AND METHODS

Mta1 knockout mice (Mta1-/- ) were employed to detect their reproductive phenotype. The pH value of Mta1-/- epididymal luminal fluid was measured, and the potential mechanism of MTA1 involved in regulating luminal acidification was detected in vivo and in vitro. A vasectomy model with abnormal pH of epididymal lumen was established to further detect the effect of MTA1 on epididymal luminal microenvironment.

RESULTS

Mta1-/- mice were fertile without any detectable defects in spermatogenesis or sperm motility while the deficiency of MTA1 could acidify the initial segment of epididymis to a certain extent. MTA1 could interact with estrogen receptor alpha (ERα) and inhibit the transcription of ERα target gene, hydrogen exchanger 3 (NHE3), and ultimately affect the epididymal luminal milieu. After vasectomy, the Mta1-/- mice presented a more acidic epididymal lumen which was closer to the normal state compared to the wild-type model.

DISCUSSION AND CONCLUSION

MTA1 is dispensable for male fertility in mice, but plays a potentially important function in regulating luminal acidification of the epididymis.

Prognostic and clinical significance of metastasis-associated gene 1 overexpression in solid cancers: A meta-analysis

BACKGROUND

In the past 2 decades, metastasis-associated gene 1 (MTA1) has attracted attention for its close association with cancer progression and its roles in chromatin remodeling processes, making it a central gene in cancer. The present meta-analysis was performed to assess MTA1 expression in solid tumors.

MATERIALS AND METHODS

This analysis identified studies that evaluated the relationship between MTA1 expression and clinical characteristics or prognosis of patients with solid tumors via the PubMed, Cochrane Library, and Embase electronic databases. Fixed-effect and random-effect meta-analytical techniques were used to correlate MTA1 expression with outcome measures. The outcome variables are shown as odds ratio (OR) or hazard ratio (HR) with 95% confidence interval (CI).

RESULTS

Analysis of 40 cohort studies involving 4564 cancer patients revealed a significant association of MTA1 overexpression with tumor patient age (>50 vs. <50 years: combined OR 0.73, 95% CI 0.57-0.94), tumor grade (G3/4 vs. G1/2: combined OR 1.94, 95% CI 1.48-2.53), tumor size (>3 cm vs. <3 cm: combined OR 2.35, 95% CI 1.73-3.19), T stage (T3/4 vs. T1/2: combined OR 2.11, 95% CI 1.74-2.56), lymph node metastasis (yes vs. no: combined OR 2.92, 95% CI 2.26-3.75), distant metastasis (yes vs. no: combined OR 2.26, 95% CI 1.42-3.59), TNM stage (III/IV vs. I/II: combined OR 2.50, 95% CI 1.84-3.38), vascular invasion (yes vs. no: combined OR 2.26, 95% CI 1.92-3.56), and poor overall survival time (HR 1.83; 95% CI: 1.53-2.20; P = .000).

CONCLUSIONS

Our analyses demonstrate that MTA1 was an effective predictor of a worse prognosis in tumor patients. Moreover, MTA1 may play important role in tumor progression and outcome, and targeting MTA1 may be a new strategy for anti-cancer therapy.

SPEN protein expression and interactions with chromatin in mouse testicular cells

SPEN (spen family transcription repressor) is a nucleic acid-binding protein putatively involved in repression of gene expression. We hypothesized that SPEN could be involved in general downregulation of the transcription during the heat shock response in mouse spermatogenic cells through its interactions with chromatin. We documented predominant nuclear localization of the SPEN protein in spermatocytes and round spermatids, which was retained after heat shock. Moreover, the protein was excluded from the highly condensed chromatin. Chromatin immunoprecipitation experiments clearly indicated interactions of SPEN with chromatinin vivo. However, ChIP-Seq analyses did not reveal any strong specific peaks both in untreated and heat shocked cells, which might suggest dispersed localization of SPEN and/or its indirect binding to DNA. Usingin situproximity ligation assay we found closein vivoassociations of SPEN with MTA1 (metastasis-associated 1), a member of the nucleosome remodeling complex with histone deacetylase activity, which might contribute to interactions of SPEN with chromatin.

Protein kinase D1 regulates subcellular localisation and metastatic function of metastasis-associated protein 1

BACKGROUND

Cancer progression and metastasis is profoundly influenced by protein kinase D1 (PKD1) and metastasis-associated protein 1 (MTA1) in addition to other pathways. However, the nature of regulatory relationship between the PKD1 and MTA1, and its resulting impact on cancer metastasis remains unknown. Here we present evidence to establish that PKD1 is an upstream regulatory kinase of MTA1.

METHODS

Protein and mRNA expression of MTA1 in PKD1-overexpressing cells were determined using western blotting and reverse-transcription quantitative real-time PCR. Immunoprecipitation and proximity ligation assay (PLA) were used to determine the interaction between PKD1 and MTA1. PKD1-mediated nucleo-cytoplasmic export and polyubiquitin-dependent proteosomal degradation was determined using immunostaining. The correlation between PKD1 and MTA1 was determined using intra-tibial, subcutaneous xenograft, PTEN-knockout (PTEN-KO) and transgenic adenocarcinoma of mouse prostate (TRAMP) mouse models, as well as human cancer tissues.

RESULTS

We found that MTA1 is a PKD1-interacting substrate, and that PKD1 phosphorylates MTA1, supports its nucleus-to-cytoplasmic redistribution and utilises its N-terminal and kinase domains to effectively inhibit the levels of MTA1 via polyubiquitin-dependent proteosomal degradation. PKD1-mediated downregulation of MTA1 was accompanied by a significant suppression of prostate cancer progression and metastasis in physiologically relevant spontaneous tumour models. Accordingly, progression of human prostate tumours to increased invasiveness was also accompanied by decreased and increased levels of PKD1 and MTA1, respectively.

CONCLUSIONS

Overall, this study, for the first time, establishes that PKD1 is an upstream regulatory kinase of MTA1 status and its associated metastatic activity, and that the PKD1-MTA1 axis could be targeted for anti-cancer strategies.

Metastasis-Associated Protein 1 Deficiency Results in Compromised Pulmonary Alveolar Capillary Angiogenesis in Mice

Background

The aim of this study was to investigate the effects of metastasis-associated protein 1 (MTA1) deficiency during angiogenesis of pulmonary alveolar capillaries in mice and to determine the molecular mechanisms involved.

Material/Methods

The expressions of MTA1, CD34, vascular endothelial growth factor (VEGF), alpha smooth muscle actin (α-SMA), and HIF-1α were analyzed in the lungs of MTA1-knockout (KO) and wild-type mice at embryonic day 18.5 and 2 months by quantitative PCR, immunoblotting, and immunohistochemistry. The morphological changes were investigated during pulmonary alveolar capillary formation. The heart weight/body weight (HW/BW) ratio and the size of the right ventricular wall cardiomyocytes were also measured. Regulation of MTA1 on HIF-1α was determined in vitro.

Results

MTA1 deficiency reduced the number of pulmonary alveolar capillaries compared to the wild-type mice. MTA1-KO mice exhibited a decreased expression of HIF-1α and VEGF in the lungs. The retarded growth of the MTA1-KO mice was also noticed during the first week after birth. Accordingly, MTA1 deficiency resulted in increased infant mortality. In surviving adult mice, MTA1 deficiency induced myocardial hypertrophy, highlighted by an increased heart weight/body weight ratio and larger cardiomyocytes. In cultured cells, HIF-1α and VEGF levels were significantly upregulated upon MTA1 overexpression, suggesting a close relationship between all 3 molecules.

Conclusions

MTA1 participates in the formation of pulmonary capillaries via stabilization of HIF-1α. This finding sheds new light on the function of MTA1 in lung development, opening new avenues for the diagnosis/treatment of related pulmonary diseases.

Colocalization of metastasis-associated proteins 1/2 and estrogen receptor alpha in rat epididymis

It has been suggested that metastasis-associated proteins 1 and 2 (MTA1 and MTA2) are capable of suppressing estrogen receptor alpha (ERα) transactivation activity in breast cancer cells. ERα, which is present in the epididymis, is a crucial mediator of maintaining the luminal environment necessary for proper sperm maturation and function. The present study was undertaken to analyze the expression profile of both MTA1 and MTA2 in the epididymis of rats and to ascertain whether MTA1/2 colocalizes with ERα in the epididymis and primary cultured epididymal epithelial cells. Reverse transcription polymerase chain reaction (RT-PCR), Western blotting and immunohistochemistry analyses were utilized to demonstrate that MTA1 and MTA2 are expressed in the epididymis. Furthermore, these analyses revealed that MTA1 and MTA2 are predominantly localized in the nuclei of almost all epididymal epithelial cells. Immunofluorescence staining revealed that MTA1/2 colocalizes with ERα in epididymal epithelial cells. In conclusion, MTA1 and MTA2 are expressed in the epididymis of rats; these proteins colocalize with ERα in epididymal epithelial cells, suggesting that MTA1 and MTA2 may be involved in the regulation of ERα transactivation activity in the epididymis of rats to facilitate a stable environment in the lumen.

MTA1 regulates higher-order chromatin structure and histone H1-chromatin interaction in-vivo

In the current study, for the first time, we found that metastasis-associated gene 1 (MTA1) was a higher-order chromatin structure organizer that decondenses the interphase chromatin and mitotic chromosomes. MTA1 interacts dynamically with nucleosomes during the cell cycle progression, prominently contributing to the mitotic chromatin/chromosome structure transitions at both prophase and telophase. We showed that the decondensation of interphase chromatin by MTA1 was independent of Mi-2 chromatin remodeling activity. H1 was reported to stabilize the compact higher-order chromatin structure through its interaction with DNA. Our data showed that MTA1 caused a reduced H1-chromatin interaction in-vivo. Moreover, the dynamic MTA1-chromatin interaction in the cell cycle contributed to the periodical H1-chromatin interaction, which in turn modulated chromatin/chromosome transitions. Although MTA1 drove a global decondensation of chromatin structure, it changed the expression of only a small proportion of genes. After MTA1 overexpression, the up-regulated genes were distributed in clusters along with down-regulated genes on chromosomes at parallel frequencies.

Molecular functions and significance of the MTA family in hormone-independent cancer

The members of the metastasis-associated protein (MTA) family play pivotal roles in both physiological and pathophysiological processes, especially in cancer development and metastasis, and their role as master regulators has come to light. Due to the fact that they were first identified as crucial factors in estrogen receptor-mediated breast cancer metastasis, most of the early studies focused on their hormone-dependent functions. However, the accumulating evidence shows that the members of MTA family are deregulated in most, if not all, the cancers studied so far. Therefore, the levels as well as the activities of the MTA family members are widely accepted as potential biomarkers for diagnosis, prognosis, and predictors of overall survival. They function differently in different cancers with specific mechanisms. p53 and HIF-1α appear to be the respectively common upstream and downstream regulator of the MTA family in both development and metastasis of a wide spectrum of cancers. Here, we review the expression and clinical significance of the MTA family, focusing on hormone-independent cancers. To illustrate the molecular mechanisms, we analyze the MTA family-related signaling pathways in different cancers. Finally, targeting the MTA family directly or the pathways involved in the MTA family indirectly could be invaluable strategies in the development of cancer therapeutics.

Physiological functions of MTA family of proteins

Although the functional significance of the metastasic tumor antigen (MTA) family of chromatin remodeling proteins in the pathobiology of cancer is fairly well recognized, the physiological role of MTA proteins continues to be an understudied research area and is just beginning to be recognized. Similar to cancer cells, MTA1 also modulates the expression of target genes in normal cells either by acting as a corepressor or coactivator. In addition, physiological functions of MTA proteins are likely to be influenced by its differential expression, subcellular localization, and regulation by upstream modulators and extracellular signals. This review summarizes our current understanding of the physiological functions of the MTA proteins in model systems. In particular, we highlight recent advances of the role MTA proteins play in the brain, eye, circadian rhythm, mammary gland biology, spermatogenesis, liver, immunomodulation and inflammation, cellular radio-sensitivity, and hematopoiesis and differentiation. Based on the growth of knowledge regarding the exciting new facets of the MTA family of proteins in biology and medicine, we speculate that the next burst of findings in this field may reveal further molecular regulatory insights of non-redundant functions of MTA coregulators in the normal physiology as well as in pathological conditions outside cancer.

Metastatic tumor antigen in hepatocellular carcinoma: golden roads toward personalized medicine

Hepatocellular carcinoma (HCC), a prototype of hypervascular tumors, is one of the most common malignancies in the world, especially hyperendemic in the Far East where chronic hepatitis B virus (HBV) infection is highly prevalent. It is characterized by the clinical feature of a poor prognosis or a high mortality due to its already far advanced stages at diagnosis. It is so multifactorial that hepatocarcinogenesis cannot be explained by a single molecular mechanism. To date, a number of pathways have been known to contribute to the development, growth, angiogenesis, and even metastasis of HCC. Among the various factors, metastatic tumor antigens (MTAs) or metastasis-associated proteins have been vigorously investigated as an intriguing target in the field of hepatocarcinogenesis. According to recent studies including ours, MTAs are not only involved in the HCC development and growth (molecular carcinogenesis), but also closely associated with the post-operative recurrence and a poor prognosis or a worse response to post-operative anti-cancer therapy (clinical significance). Herein, we review MTAs in light of their essential structure, functions, and molecular mechanism in hepatocarcinogenesis. We will also focus in detail on the interaction between hepatitis B x protein (HBx) of HBV and MTA in order to clarify the HBV-associated HCC development. Finally, we will discuss the prognostic significance and clinical application of MTA in HCC. We believe that this review will help clinicians to understand the meaning and use of the detection of MTA in order to more effectively manage their HCC patients.

Function and regulation of MTA1 and MTA3 in malignancies of the female reproductive system

The family of metastasis-associated (MTA) genes is a small group of transcriptional co-regulators which are involved in various physiological functions, ranging from lymphopoietic cell differentiation to the development and maintenance of epithelial cell adhesions. By recruiting histone-modifying enzymes to specific promoter sequences, MTA proteins can function both as transcriptional repressors and activators of a number of cancer-relevant proteins, including Snail, E-cadherin, signal transducer and activator of transcriptions (STATs), and the estrogen receptor. Their involvement in the epithelial-mesenchymal transition process and regulatory interactions with estrogen receptor activity has made MTA proteins highly interesting research candidates, especially in the field of hormone-sensitive breast cancer and malignancies of the female reproductive tract. This review focuses on the current knowledge about the function and regulation of MTA1 and MTA3 proteins in gynecological cancer, including ovarian, endometrial, and cervical tumors.

Clinical implications of MTA proteins in human cancer

Metastasis-associated gene or metastasis tumor antigen 1 (MTA1) is a new member of cancer progression-related gene family. It was first identified in rat mammary adenocarcinoma and later recognized as an important constituent of nucleosomal remodeling complex (NuRD), displaying dual regulatory functions as a co-repressor and co-activator for a large number of genes. Chromatin remodelers are ATP-dependent multi-protein chromatin modifying machines. These complexes alter the nucleosome positioning regulating the accessibility of genomic DNA to various transcription factors and thus modulate eukaryotic gene transcription. Since its identification two decades ago, MTA1 has been reported to be overexpressed in many cancers. Moreover, its overexpression has also been correlated with transformation and tumor progression. Furthermore, MTA1 has been shown to modulate the response of several tumor suppressor genes like p53 and oncogenes like c-myc. Taken together, current literature suggests that MTA proteins, especially MTA1, act as a master co-regulatory molecule involved in the carcinogenesis and progression of various malignant tumors. The primary focus of this review is to provide an overview of the MTA proteins with special emphasis on its role in cancer and use as a marker for cancer progression and potential target for therapy.

Role of MTA1 in cancer progression and metastasis

The MTA1 protein contributes to the process of cancer progression and metastasis through multiple genes and protein targets and interacting proteins with roles in transformation, anchorage-independent growth, invasion, survival, DNA repair, angiogenesis, hormone independence, metastasis, and therapeutic resistance. Because the roles and clinical significance of MTA proteins in human cancer are discussed by other contributors in this issue, this review will focus on our current understanding of the underlying principles of action behind the biological effects of MTA1. MTA proteins control a spectrum of cancer-promoting processes by modulating the expression of target genes and/or the activity of MTA-interacting proteins. In the case of MTA1, these functions are manifested through posttranslational modifications of MTA1 in response to upstream signals, MTA1 interaction with binding proteins, and the expression of target gene products. Studies delineating the molecular basis of dual functionality of MTA1 reveal that the functions of MTA1-chromatin-modifying complexes in the context of target gene regulation are dynamic in nature. The nature and targets of MTA1-chromatin-modifying complexes are also governed by the dynamic plasticity of the nucleosome landscape as well as kinetics of activation and inactivation of enzymes responsible for posttranslational modifications on the MTA1 protein. These broadly applicable functions also explain why MTA1 may be a "hub" gene in cancer. Because the deregulation of enzymes and their substrates with roles in MTA1 biology is not necessarily limited to cancer, we speculate that the lessons from MTA1 as a prototype dual master coregulator will be relevant for other human diseases. In this context, the concept of the dynamic nature of corepressor versus coactivator complexes and the MTA1 proteome as a function of time to signal is likely to be generally applicable to other multiprotein regulatory complexes in living systems.

Subcellular localization of MTA proteins in normal and cancer cells

The subcellular localization of a protein is closely linked to and indicates its function. The metastatic tumor antigen (MTA) family has been under continuous investigation since its identification two decades ago. MTA1, MTA2, and MTA3 are the main members of the MTA family. MTA1, as the representative member of this family, has been shown to be widely expressed in both embryonic and adult tissues, as well as in normal and cancerous conditions, indicating that MTA1 has functions both in physiological and pathological contexts. MTA1 is expressed at a higher level in most cancers than in their normal tissue counterparts. Even in normal cells, MTA1 levels vary a great deal from tissue to tissue. Importantly, MTA1 shows a multiple localization pattern in the cell, as do MTA2 and MTA3. Different MTA components in different subcellular compartments may exert different molecular functions in the cell. Previous studies revealed that MTA1 and MTA2 are predominately localized to the nucleus, while MTA3 is observed in both the nucleus and cytoplasm. Recent studies have reported that MTA1 is located in the nucleus, cytoplasm, and the nuclear envelope. In the nucleus, MTA1 dynamically interacts with chromatin in a MTA1-K532 methylation-dependent manner, whereas cytoplasmic MTA1 binds to the microtubule skeleton. MTA1 also shows a dynamic distribution during the cell cycle. Further investigations are needed to identify the exact subcellular localizations of MTA proteins. We review the sub-cellular localization patterns of the MTA family members and give a comprehensive overview of their respective molecular activities in multiple contexts.

Insight into the architecture of the NuRD complex: structure of the RbAp48-MTA1 subcomplex

The nucleosome remodeling and deacetylase (NuRD) complex is a widely conserved transcriptional co-regulator that harbors both nucleosome remodeling and histone deacetylase activities. It plays a critical role in the early stages of ES cell differentiation and the reprogramming of somatic to induced pluripotent stem cells. Abnormalities in several NuRD proteins are associated with cancer and aging. We have investigated the architecture of NuRD by determining the structure of a subcomplex comprising RbAp48 and MTA1. Surprisingly, RbAp48 recognizes MTA1 using the same site that it uses to bind histone H4, showing that assembly into NuRD modulates RbAp46/48 interactions with histones. Taken together with other results, our data show that the MTA proteins act as scaffolds for NuRD complex assembly. We further show that the RbAp48-MTA1 interaction is essential for the in vivo integration of RbAp46/48 into the NuRD complex.

The subcellular distribution and function of MTA1 in cancer differentiation

The functions and mechanisms of metastasis-associated protein 1 (MTA1) in cancer progression are still unclear due to a lagged recognition of the subcellular localization. In the present study, using multiple molecular technologies we confirmed for the first time that MTA1 localizes to the nucleus, cytoplasm and nuclear envelope. MTA1 is primarily localized in the nucleus of normal adult tissues but in the cytoplasm of embryonic tissues. While in colon cancer, both distributions have been described. Further investigation revealed that MTA1 localizes on the nuclear envelope in a translocated promoter region (TPR)-dependent manner, while in the cytoplasm, MTA1 shows an obvious localization on microtubules. Both nuclear and cytoplasmic MTA1 are associated with cancer progression. However, these functions may be associated with different mechanisms because only nuclear MTA1 has been associated with cancer differentiation. Overexpression of MTA1 in HCT116 cells inhibited differentiation and promoted proliferation, whereas MTA1 knockdown resulted in cell differentiation and death. Theses results not only suggest that nuclear MTA1 is a good marker for cancer differentiation diagnosis and a potential target for the treatment of cancers but also reveal the necessity to differentially examine the functions of nuclear and cytoplasmic MTA1.

Effects of antioxidants on drugs used against testicular cancer-induced alterations in metastasis-associated protein 1 signaling in the rat testis

Metastasis-associated protein 1 (MTA1) is involved in tumor growth and metastasis of cancers. Being a component of nucleosome remodeling and histone deacetylase complex, the protein is also associated with DNA damage response pathway. Since the protein is involved in cancer pathology, we first investigated the effects of bleomycin, etoposide, and cisplatin (BEP) on MTA1 signaling in the testis. Second, since the antioxidants (AOs) have protective effects, we further investigated whether or not an AO cocktail modulates the effects of the drugs. Adult male Sprague Dawley rats ( N = 4) were treated either with saline, or AO (α-tocopherol, l-ascorbic acid, zinc, and selenium), or therapeutic dose levels of etoposide (15 mg/kg) and cisplatin (3 mg/kg) from day 1–4 of the week and B (1.5 mg/kg) on the second day of the week, or BEP + AO. The real-time polymerase chain reaction showed that MTA1 and MTA1s (short form) gene expression was downregulated in AO (100% and 100%), BEP (86% and 71%), and BEP + AO (97% and 93%) groups. Western blotting and immunohistochemistry results showed that unnormalized MTA1 protein expression was upregulated in AO (38%) and BEP + AO (34%) groups; however, the MTA1/β-actin ratio was upregulated in all treated groups (21, 19, and 15%, respectively). In conclusion, the results indicate that both BEP and AO suppress MTA1 and MTA1s transcription, which may render the germ cells to be more prone to apoptosis. However, upregulation of MTA1 protein expression may be related to induced DNA damage. Modulation of MTA1 signaling is a novel mechanism of action of BEP and AO, which may be useful in developing newer anticancer drugs.

Presence of metastasis-associated protein 1 in Sertoli cells is required for proper contact between Sertoli cells and adjacent germ cells

OBJECTIVE

To investigate whether the normal expression of metastasis-associated protein 1 (MTA1) in Sertoli cells (SCs) is associated with adjacent germ cells (GCs) and to provide the functional relevance of MTA1 in this somatic cell.

METHODS

The expression pattern of MTA1 in the SCs of impaired human spermatogenesis was determined using immunohistochemistry. The effect of the depletion of GCs on the expression of MTA1 in isolated SCs was evaluated using reverse transcriptase polymerase chain reaction in murine testes treated with busulphan. Finally, using multiple assays, the functional investigation of MTA1 by its specific knockdown was performed in SC-GC co-cultures.

RESULTS

SCs were negatively immunolabeled in the tubules with impaired spermatogenesis. Depletion of murine GCs by treatment with busulphan resulted in a dramatic decrease of the MTA1 transcripts level in the isolated SCs on the 15th day of treatment and thereafter had totally abolished MTA1 expression by the 30th day of treatment, respectively. The addition of isolated round spermatids into SC culture could partially elevate MTA1 expression in the latter. Furthermore, MTA1 is crucial to maintain the GC nursery function and normal anchoring junction formation in SCs because ablation of MTA1 by siRNA induced extensive defects of genes related to SC homeostasis.

CONCLUSION

We propose a novel role for SC-expressing MTA1, which is determined by the presence of surrounding GCs, in mediating the crosstalk between SCs and GCs by influencing a broad spectrum of gene changes.

Metastasis-associated protein 1 is an integral component of the circadian molecular machinery

The mammalian circadian clock regulates the daily cycles of many important physiological processes, but its mechanism is not well understood. Here we provide genetic and biochemical evidence that metastasis-associated protein 1 (MTA1), a widely upregulated gene product in human cancers, is an integral component of the circadian molecular machinery. Knockout of MTA1 in mice disrupts the free-running period of circadian rhythms under constant light and normal entrainment of behaviour to 12-h-light/12-h-dark cycles. The CLOCK-BMAL1 heterodimer activates MTA1 transcription through a conserved E-box element at its promoter. MTA1, in turn, interacts with and recruits CLOCK-BMAL1 at its own and CRY1 promoters and promotes their transcription. Moreover, MTA1 deacetylates BMAL1 at lysine 538 through regulating deacetylase SIRT1 expression, thus disturbing the CRY1-mediated negative feedback loop. These findings uncover a previously unappreciated role for MTA1 in maintenance of circadian rhythmicity through acting on the positive limb of the clock machinery.

Metastasis-associated protein 1/nucleosome remodeling and histone deacetylase complex in cancer

Cancer cells frequently exhibit deregulation of coregulatory molecules to drive the process of growth and metastasis. One such group of ubiquitously expressed coregulators is the metastasis-associated protein (MTA) family, a critical component of the nucleosome remodeling and histone deacetylase (NuRD) complex. MTA1 occupies a special place in cancer biology because of its dual corepressor or coactivator nature and widespread overexpression in human cancers. Here, we highlight recent advances in our understanding of the vital roles of MTA1 on transformation, epithelial-mesenchymal transition, and the functions of key cancer-relevant molecules such as a nexus of multiple oncogenes and tumor suppressors. In addition to its paramount role in oncogenesis, we reveal several new physiologic functions of MTA1 related to DNA damage, inflammatory responses, and infection, in which MTA1 functions as a permissive "gate keeper" for cancer-causing parasites. Further, these discoveries unraveled the versatile multidimensional modes of action of MTA1, which are independent of the NuRD complex and/or transcription. Given the emerging roles of MTA1 in DNA repair, inflammation, and parasitism, we discuss the possibility of MTA1-targeted therapy for use not only in combating cancer but also in other inflammation and pathogen-driven pathologic conditions.

Localization and androgen regulation of metastasis-associated protein 1 in mouse epididymis

BACKGROUND

Metastasis-associated protein 1 (MTA1), the founding member of the MTA family of genes, can modulate transcription by influencing the status of chromatin remodeling. Despite its strong correlation with the metastatic potential of cancer cells, MTA1 can also regulate crucial cellular pathways by modifying the acetylation status. We have previously reported the presence of MTA1/MTA1 in human and mouse testes, providing the evidence for its involvement in the regulation of testicular function during murine spermatogenesis. The objective of present study was to further assess the localization of MTA1 in mouse epididymis on both transcriptional and translational level, and then to explore whether MTA1 expression is regulated by androgens and postnatal epididymal development.

METHODOLOGY/PRINCIPAL FINDINGS

Mice were deprived of circulating androgen by bilaterally castration and were then supplemented with exogenous testosterone propionate for one week. MTA1 was immunolocalized in the epithelium of the entire epididymis with the maximal expression in the nuclei of principal cells and of clear cells in proximal region. Its expression decreased gradually after castration, whereas testosterone treatment could restore the expression, indicating that the expression of this gene is dependent on androgen. During postnatal development, the protein expression in the epididymis began to appear from day 7 to day 14, increased dramatically from postnatal day 28, and peaked at adulthood onwards, coinciding with both the well differentiated status of epididymis and the mature levels of circulating androgens. This region- and cell-specific pattern was also conservative in normal human epididymis.

CONCLUSIONS

Our data suggest that the expression of MTA1 protein could be regulated by androgen pathway and its expression level is closely associated with the postnatal development of the epididymis, giving rise to the possibility that this gene plays a potential role in sperm maturation and fertility.