The Meq oncoprotein of Marek's disease virus interacts with p53 and inhibits its transcriptional and apoptotic activities

<p>Abstract</p> <p>Background</p> <p>Marek's disease virus (MDV) is an oncogenic herpesvirus, which causes malignant lymphoma in chickens. The Meq protein of MDV, which is expressed abundantly in MDV-infected cells and in Marek's disease (MD) tumor cells, functions as a transcriptional activator and has been proposed to play an important role in oncogenic transformation. Preliminary studies demonstrated that Meq is able to bind p53 <it>in vitro</it>, as demonstrated using a protein-binding assay. This observation prompted us to examine whether the interaction between Meq and p53 occurs in cells, and to investigate the biological significance of this interaction.</p> <p>Results</p> <p>We confirmed first that Meq interacted directly with p53 using a yeast two-hybrid assay and an immunoprecipitation assay, and we investigated the biological significance of this interaction subsequently. Exogenous expression of Meq resulted in the inhibition of p53-mediated transcriptional activity and apoptosis, as analyzed using a p53 luciferase reporter assay and a TUNEL assay. The inhibitory effect of Meq on transcriptional activity mediated by p53 was dependent on the physical interaction between these two proteins, because a Meq deletion mutant that lacked the p53-binding region lost the ability to inhibit p53-mediated transcriptional activity and apoptosis. The Meq variants L-Meq and S-Meq, but not VS-Meq and ∆Meq, which were expressed in MD tumor cells and MDV-infected cells, exerted an inhibitory effect on p53 transcriptional activity. In addition, ∆Meq was found to act as a negative regulator of Meq.</p> <p>Conclusions</p> <p>The Meq oncoprotein interacts directly with p53 and inhibits p53-mediated transcriptional activity and apoptosis. These findings provide valuable insight into the molecular basis for the function of Meq in MDV oncogenesis.</p

Argininosuccinate Lyase Deficiency Causes Blood-Brain Barrier Disruption via Nitric Oxide-Mediated Dysregulation of Claudin Expression

Nitric oxide (NO) is a critical signaling molecule that has been implicated in the pathogenesis of neurocognitive diseases. Both excessive and insufficient NO production have been linked to pathology. Previously, we have shown that argininosuccinate lyase deficiency (ASLD) is a novel model system to investigate cell-autonomous, nitric oxide synthase-dependent NO deficiency. Humans with ASLD are at increased risk for developing hyperammonemia due to a block in ureagenesis. However, natural history studies have shown that individuals with ASLD have multisystem disease including neurocognitive deficits that can be independent of ammonia. Here, using ASLD as a model of NO deficiency, we investigated the effects of NO on brain endothelial cells in vitro and the blood-brain barrier (BBB) in vivo. Knockdown of ASL in human brain microvascular endothelial cells (HBMECs) led to decreased transendothelial electrical resistance, indicative of increased cell permeability. Mechanistically, treatment with an NO donor or inhibition of Claudin-1 improved barrier integrity in ASL-deficient HBMECs. Furthermore, in vivo assessment of a hypomorphic mouse model of ASLD showed increased BBB leakage, which was partially rescued by NO supplementation. Our results suggest that ASL-mediated NO synthesis is required for proper maintenance of brain microvascular endothelial cell functions as well as BBB integrity

ATRX Silences Cartpt Expression in Osteoblastic Cells During Skeletal Development

ATP-dependent chromatin remodeling protein ATRX is an essential regulator involved in maintenance of DNA structure and chromatin state and regulation of gene expression during development. ATRX was originally identified as the monogenic cause of X-linked α-thalassemia mental retardation (ATR-X) syndrome. Affected individuals display a variety of developmental abnormalities and skeletal deformities. Studies from others investigated the role of ATRX in skeletal development by tissue-specific Atrx knockout. However, the impact of ATRX during early skeletal development has not been examined. Using preosteoblast-specific Atrx conditional knockout mice, we observed increased trabecular bone mass and decreased osteoclast number in bone. In vitro coculture of Atrx conditional knockout bone marrow stromal cells (BMSCs) with WT splenocytes showed impaired osteoclast differentiation. Additionally, Atrx deletion was associated with decreased receptor activator of nuclear factor κ-B ligand (Rankl)/ osteoprotegerin (Opg) expression ratio in BMSCs. Notably, Atrx-deficient osteolineage cells expressed high levels of the neuropeptide cocaine- and amphetamine-regulated transcript prepropeptide (Cartpt). Mechanistically, ATRX suppresses Cartpt transcription by binding to the promoter, which is otherwise poised for Cartpt expression by RUNX2 binding to the distal enhancer. Finally, Cartpt silencing in Atrx conditional knockout BMSCs rescued the molecular phenotype by increasing the Rankl/Opg expression ratio. Together, our data show a potent repressor function of ATRX in restricting Cartpt expression during skeletal development

Minireview: Nuclear Receptor Regulation of Osteoclast and Bone Remodeling

Osteoclasts are bone-resorbing cells essential for skeletal remodeling and regeneration. However, excessive osteoclasts often contribute to prevalent bone degenerative diseases such as osteoporosis, arthritis, and cancer bone metastasis. Osteoclast dysregulation is also associated with rare disorders such as osteopetrosis, pycnodysostosis, Paget's disease, and Gorham-Stout syndrome. The nuclear receptor (NR) family of transcription factors functions as metabolic sensors that control a variety of physiological processes including skeletal homeostasis and serves as attractive therapeutic targets for many diseases. In this review, we highlight recent findings on the new players and the new mechanisms for how NRs regulate osteoclast differentiation and bone resorption. An enhanced understanding of NR functions in osteoclastogenesis will facilitate the development of not only novel osteoprotective medicine but also prudent strategies to minimize the adverse skeletal effects of certain NR-targeting drugs for a better treatment of cancer and metabolic diseases

The research on operational reliability evaluation of straddle-type monorail vehicle

In order to master the main malfunction and the law of occurrence of the vehicle which affects the operational reliability of the Straddle-Type Monorail traffic, this paper, based on the structural characteristics of monorail vehicle system and the statistical data of vehicle operational malfunction, uses the analysis method of system reliability engineering to study and determine the key factors that affect the operational reliability of monorail vehicle. Then, the operational reliability evaluation index system of monorail vehicle is established based on the influencing factors. Finally, the AHP (Analytic Hierarchy Process) method is used to determine the weights of each index, and the fuzzy comprehensive evaluation method is used to evaluate the operational reliability of monorail vehicle synthetically. The evaluation results have some guidance on the development of more effective maintenance strategies for monorail vehicle maintenance departments

Mitochondrial Complex I Activity Suppresses Inflammation and Enhances Bone Resorption by Shifting Macrophage-Osteoclast Polarization

SummaryMitochondrial complex I (CI) deficiency is associated with multiple neurological and metabolic disorders. However, its effect on innate immunity and bone remodeling is unclear. Using deletion of the essential CI subunit Ndufs4 as a model for mitochondrial dysfunction, we report that mitochondria suppress macrophage activation and inflammation while promoting osteoclast differentiation and bone resorption via both cell-autonomous and systemic regulation. Global Ndufs4 deletion causes systemic inflammation and osteopetrosis. Hematopoietic Ndufs4 deletion causes an intrinsic lineage shift from osteoclast to macrophage. Liver Ndufs4 deletion causes a metabolic shift from fatty acid oxidation to glycolysis, accumulating fatty acids and lactate (FA/LAC) in the circulation. FA/LAC further activates Ndufs4−/− macrophages via reactive oxygen species induction and diminishes osteoclast lineage commitment in Ndufs4−/− progenitors; both inflammation and osteopetrosis in Ndufs4−/− mice are attenuated by TLR4/2 deletion. Together, these findings reveal mitochondrial CI as a critical rheostat of innate immunity and skeletal homeostasis

Orexin Regulates Bone Remodeling via a Dominant Positive Central Action and a Subordinate Negative Peripheral Action

SummaryOrexin neuropeptides promote arousal, appetite, reward, and energy expenditure. However, whether orexin affects bone mass accrual is unknown. Here, we show that orexin functions centrally through orexin receptor 2 (OX2R) in the brain to enhance bone formation. OX2R null mice exhibit low bone mass owing to elevated circulating leptin, whereas central administration of an OX2R-selective agonist augments bone mass. Conversely, orexin also functions peripherally through orexin receptor 1 (OX1R) in the bone to suppress bone formation. OX1R null mice exhibit high bone mass owing to a differentiation shift from marrow adipocyte to osteoblast that results from higher osseous ghrelin expression. The central action is dominant because bone mass is reduced in orexin null and OX1R2R double null mice but enhanced in orexin-overexpressing transgenic mice. These findings reveal orexin as a critical rheostat of skeletal homeostasis that exerts a yin-yang dual regulation and highlight orexin as a therapeutic target for osteoporosis

Temporal transcriptomic landscape of postnatal mouse ovaries reveals dynamic gene signatures associated with ovarian aging

Abstract The ovary is the most important organ for maintaining female reproductive health, but it fails before most other organs. Aging-associated alterations in gene expression patterns in mammalian ovaries remain largely unknown. In this study, the transcriptomic landscape of postnatal mouse ovaries over the reproductive lifespan was investigated using bulk RNA sequencing in C57BL/6 mice. Gene expression dynamics revealed that the lifespan of postnatal mouse ovaries comprised four sequential stages, during which 2517 genes were identified as differentially enriched. Notably, the DNA repair pathway was found to make a considerable and specific contribution to the process of ovarian aging. Temporal gene expression patterns were dissected to identify differences in gene expression trajectories over the lifespan. In addition to DNA repair, distinct biological functions (including hypoxia response, epigenetic modification, fertilization, mitochondrial function, etc.) were overrepresented in particular clusters. Association studies were further performed to explore the relationships between known genes responsible for ovarian function and differentially expressed genes identified in this work. We found that the causative genes of human premature ovarian insufficiency were specifically enriched in distinct gene clusters. Taken together, our findings reveal a comprehensive transcriptomic landscape of the mouse ovary over the lifespan, providing insights into the molecular mechanisms underlying mammalian ovarian aging and supporting future etiological studies of aging-associated ovarian disorders.</jats:p