NuA4 and H2A.Z control environmental responses and autotrophic growth in Arabidopsis

Nucleosomal acetyltransferase of H4 (NuA4) is an essential transcriptional coactivator in eukaryotes, but remains poorly characterized in plants. Here, we describe Arabidopsis homologs of the NuA4 scaffold proteins Enhancer of Polycomb-Like 1 (AtEPL1) and Esa1-Associated Factor 1 (AtEAF1). Loss of AtEAF1 results in inhibition of growth and chloroplast development. These effects are stronger in the Atepl1 mutant and are further enhanced by loss of Golden2-Like (GLK) transcription factors, suggesting that NuA4 activates nuclear plastid genes alongside GLK. We demonstrate that AtEPL1 is necessary for nucleosomal acetylation of histones H4 and H2A.Z by NuA4 in vitro. These chromatin marks are diminished genome-wide in Atepl1, while another active chromatin mark, H3K9 acetylation (H3K9ac), is locally enhanced. Expression of many chloroplast-related genes depends on NuA4, as they are downregulated with loss of H4ac and H2A.Zac. Finally, we demonstrate that NuA4 promotes H2A.Z deposition and by doing so prevents spurious activation of stress response genes.

Neuron-Specific Mechanisms Control the Mitochondrial Regulator PGC-1a

Mitochondrial dysfunction has been proposed as a hallmark of the aging process. Specifically, as a function of aging, mitochondria appear to have decreased enzyme activity and respiratory capacity and increase reactive oxygen species production. Brain aging is associated with morphological and homeostatic changes, including alterations in brain size, cognitive impairment, and white and grey matter integrity. However, the causes of these changes remain an open and actively pursued field of study. The ubiquitously expressed transcriptional coactivator peroxisome proliferator-activated receptor gamma-coactivator 1 (PGC-1a) has been described as the master regulator of mitochondrial function. Despite the emerging connections between PGC-1a and disease vulnerability, the regulation of PGC-1a outside of the skeletal muscle, liver, and adipose tissue is not well defined. This is particularly true in the brain, where PGC-1a is enriched in neurons, and alterations in expression levels have been linked to neurodegenerative disorders. Here we report that astrocytes and neurons differ substantially in mitochondrial status and the transcript variants of PGC-1a expressed, including using a neuron-specific promoter. Taking advantage of the ability of the tau-kinase GSK-3b to influence PGC-1a expression, we investigate how transcript variants are differentially regulated in primary neurons and astrocytes. Neuronal PGC-1a responds robustly to GSK3b inhibition by lithium, switching the dominant promoter, leading to changes in isoform distribution and abundance, while astrocytes are refractory to lithium treatment. The data presented here highlight key mechanisms for neuron-specific metabolic regulation that are likely to be relevant to neurodegenerative diseases that have a link to mitochondrial dysfunction.

The Effect of Gembili Starch (Dioscorea esculenta) and Eubacterium rectal Supplementation on Skeletal Muscle Peroxisome Proliferator-Activated Receptor γ Coactivator 1α (Pgc-1α) Expression in Diabetic Mice Models

BACKGROUND: Gembili or Dioscorea esculenta is a local food that is produced by several areas in Indonesia. Few studies have reported its health benefits for diabetes mellitus but a little is understood about its mechanism of action. PGC-1α is a transcriptional coactivator for genes that involved in energy metabolism and increased expression of this gene has previously been associated with improved insulin sensitivity. AIM: The objective of this study was to investigate the effect of Gembili starch and Gembili starch with butirogenic bacteria Eubacterium rectal on PGC-1α expression in skeletal muscle of diabetic mice. MATERIALS AND METHODS: Three months old male diabetic Wistar mice were divided into groups based on dietary supplement: Gembili starch only; Gembili starch with E. rectal; and E. rectal only. Positive (diabetic mice) and negative (non-diabetic) control groups were used in this study. After 4 weeks of supplementation, mice were sacrificed and muscle tissue was taken from musculus vastus latissimus. Plasma blood glucose was measured before and after intervention. PGC-1α expression was measured with immunohistochemistry and quantified by dividing cells that produce PGC-1α with total cells. RESULTS: Plasma blood glucose was reduced after invention in group that received Gembili starch only (p < 0.001); Gembili starch with E. rectal (p < 0.001); and E. rectal only (p < 0.001). The protein expression of PGC-1α in diabetic mice receiving Gembili starch only was significantly higher compared to control (p < 0.05). CONCLUSION: This study shown that Gembili starch supplementation was able to improve glucose control in diabetic mice and this effect was obtained perhaps through PGC-1α activation. Further study is needed to investigate the effect of Gembili starch supplementation on fat metabolism.

PV-specific loss of the transcriptional coactivator PGC-1α slows down the evolution of epileptic activity in an acute ictogenic model.

The transcriptional coactivator, PGC-1α (peroxisome proliferator activated receptor gamma coactivator 1α), plays a key role coordinating energy requirement within cells. Its importance is reflected in the growing number of psychiatric and neurological conditions that have been associated with reduced PGC-1α levels. In cortical networks, PGC-1α is required for the induction of parvalbumin (PV) expression in interneurons, and PGC-1a deficiency affects synchronous GABAergic release. It is unknown, however, how this affects cortical excitability. We show here that knocking down PGC-1α specifically in the PV-expressing cells (PGC-1αPV-/-) blocks the activity-dependent regulation of the synaptic proteins, SYT2 and CPLX1. More surprisingly, this cell-class specific knock-out of PGC-1α appears to have a novel anti-epileptic effect, as assayed in brain slices bathed in 0 Mg2+ media. The rate of occurrence of pre-ictal discharges developed approximately equivalently in wild-type and PGC-1αPV-/- brain slices, but the intensity of these discharges was lower in PGC-1αPV-/- slices, as evident from the reduced power in the gamma range and reduced firing rates in both PV interneurons and pyramidal cells during these discharges. Reflecting this reduced intensity in the pre-ictal discharges, the PGC-1αPV-/- brain slices experienced many more discharges before transitioning into a seizure-like event. Consequently, there was a large increase in the latency to the first seizure-like event in brain slices lacking PGC-1α in PV interneurons. We conclude that knocking down PGC-1α limits the range of PV interneuron firing, and this slows the pathophysiological escalation during ictogenesis.

A brain-specific pgc1α fusion transcript affects gene expression and behavioural outcomes in mice

PGC1α is a transcriptional coactivator in peripheral tissues, but its function in the brain remains poorly understood. Various brain-specific Pgc1α isoforms have been reported in mice and humans, including two fusion transcripts (FTs) with non-coding repetitive sequences, but their function is unknown. The FTs initiate at a simple sequence repeat locus ∼570 Kb upstream from the reference promoter; one also includes a portion of a short interspersed nuclear element (SINE). Using publicly available genomics data, here we show that the SINE FT is the predominant form of Pgc1α in neurons. Furthermore, mutation of the SINE in mice leads to altered behavioural phenotypes and significant up-regulation of genes in the female, but not male, cerebellum. Surprisingly, these genes are largely involved in neurotransmission, having poor association with the classical mitochondrial or antioxidant programs. These data expand our knowledge on the role of Pgc1α in neuronal physiology and suggest that different isoforms may have distinct functions. They also highlight the need for further studies before modulating levels of Pgc1α in the brain for therapeutic purposes.

PRAMEF2-mediated dynamic regulation of YAP signaling promotes tumorigenesis

PRAMEF2 is a member of the PRAME multigene family of cancer testis antigens, which serve as prognostic markers for several cancers. However, molecular mechanisms underlying its role in tumorigenesis remain poorly understood. Here, we report that PRAMEF2 is repressed under conditions of altered metabolic homeostasis in a FOXP3-dependent manner. We further demonstrate that PRAMEF2 is a BC-box containing substrate recognition subunit of Cullin 2–based E3 ubiquitin ligase complex. PRAMEF2 mediates polyubiquitylation of LATS1 kinase of the Hippo/YAP pathway, leading to its proteasomal degradation. The site for ubiquitylation was mapped to the conserved Lys860 residue in LATS1. Furthermore, LATS1 degradation promotes enhanced nuclear accumulation of the transcriptional coactivator YAP, resulting in increased expression of proliferative and metastatic genes. Thus, PRAMEF2 promotes malignant phenotype in a YAP-dependent manner. Additionally, elevated PRAMEF2 levels correlate with increased nuclear accumulation of YAP in advanced grades of breast carcinoma. These findings highlight the pivotal role of PRAMEF2 in tumorigenesis and provide mechanistic insight into YAP regulation.

Otic Neurogenesis in Xenopus laevis: Proliferation, Differentiation, and the Role of Eya1

Using immunostaining and confocal microscopy, we here provide the first detailed description of otic neurogenesis in Xenopus laevis. We show that the otic vesicle comprises a pseudostratified epithelium with apicobasal polarity (apical enrichment of Par3, aPKC, phosphorylated Myosin light chain, N-cadherin) and interkinetic nuclear migration (apical localization of mitotic, pH3-positive cells). A Sox3-immunopositive neurosensory area in the ventromedial otic vesicle gives rise to neuroblasts, which delaminate through breaches in the basal lamina between stages 26/27 and 39. Delaminated cells congregate to form the vestibulocochlear ganglion, whose peripheral cells continue to proliferate (as judged by EdU incorporation), while central cells differentiate into Islet1/2-immunopositive neurons from stage 29 on and send out neurites at stage 31. The central part of the neurosensory area retains Sox3 but stops proliferating from stage 33, forming the first sensory areas (utricular/saccular maculae). The phosphatase and transcriptional coactivator Eya1 has previously been shown to play a central role for otic neurogenesis but the underlying mechanism is poorly understood. Using an antibody specifically raised against Xenopus Eya1, we characterize the subcellular localization of Eya1 proteins, their levels of expression as well as their distribution in relation to progenitor and neuronal differentiation markers during otic neurogenesis. We show that Eya1 protein localizes to both nuclei and cytoplasm in the otic epithelium, with levels of nuclear Eya1 declining in differentiating (Islet1/2+) vestibulocochlear ganglion neurons and in the developing sensory areas. Morpholino-based knockdown of Eya1 leads to reduction of proliferating, Sox3- and Islet1/2-immunopositive cells, redistribution of cell polarity proteins and loss of N-cadherin suggesting that Eya1 is required for maintenance of epithelial cells with apicobasal polarity, progenitor proliferation and neuronal differentiation during otic neurogenesis.

Abstract P454: The Interaction Of P300 With Brg1 Acetylated The Histone H3 Globular Domain In Heart Failure

Background: Epigenetic regulatory mechanisms such as histone post-translational modifications are involved in the development of heart failure. Although the acetylation of tail domains, such as H3K9, has been extensively studied, that of H3K122, the globular domain, has received much less attention. Acetylation of the globular domain directly activates transcription by destabilizing histone-DNA binding. However, the acetylation of these domains during the transition from left ventricular hypertrophy (LVH) to heart failure (HF) remains unknown. Methods and Results: Primary cultured cardiomyocytes prepared from neonatal rats were treated with phenylephrine (PE). PE increased the acetylation of H3K9 and H3K122. The acetylation of H3K9 and H3K122 on the promoters of ANF and BNP, which are hypertrophic reaction genes, was increased in cardiomyocyte hypertrophy. To investigate whether the transcriptional coactivator p300 is involved in the acetylation of H3K9 and H3K122, p300 knockdown was used. p300 knockdown suppressed PE-induced cardiomyocyte hypertrophy and the acetylation of H3K9 and H3K122. In Dahl-salt sensitive rats, in vivo chromatin-immunoprecipitation assays revealed that the acetylation of H3K9 on the promoter of the hypertrophic response genes was significantly increased in LVH, but the acetylation of H3K122 was not increased in LVH. However, H3K122 acetylation was significantly increased in HF. On the other hand, there was no difference in the amount of recruitment of p300 in LVH and HF. Interestingly, immunoprecipitation-WB showed that binding of p300 with BRG1, a key component of the SWI/SNF complex, was enhanced in HF. The recruitment of BRG1 increased significantly in HF compared to LVH. Moreover, PFI-3, a BRG1 inhibitor, significantly suppressed a PE-induced increase in cardiomyocyte surface area, the mRNA levels of ANF and BNP, and the acetylation of H3K9 and H3K122 in cultured cardiomyocytes. Conclusion: This study demonstrates that the acetylation of H3K122 is enhanced via the interaction of p300 and BRG1 in heart failure, providing novel insights into the epigenetic regulatory mechanism governing transcriptional activity in these processes.

TAZ inhibits osteoclastogenesis by attenuating TAK1/NF-κB signaling

Osteoporosis is an osteolytic disorder commonly associated with excessive osteoclast formation. Transcriptional coactivator with PDZ-binding motif (TAZ) is a key downstream effector of the Hippo signaling pathway; it was suggested to be involved in the regulation of bone homeostasis. However, the exact role of TAZ in osteoclasts has not yet been established. In this study, we demonstrated that global knockout and osteoclast-specific knockout of TAZ led to a low-bone mass phenotype due to elevated osteoclast formation, which was further evidenced by in vitro osteoclast formation assays. Moreover, the overexpression of TAZ inhibited RANKL-induced osteoclast formation, whereas silencing of TAZ reduced it. Mechanistically, TAZ bound to TGF-activated kinase 1 (TAK1) and reciprocally inhibited NF-κB signaling, suppressing osteoclast differentiation. Collectively, our findings highlight an essential role of TAZ in the regulation of osteoclastogenesis in osteoporosis and its underlying mechanism.