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The function of the mitogen-activated protein kinase signaling pathway is required for the activation of immediate early genes (IEGs), including EGR1 and FOS, for cell growth and proliferation. Recent studies have identified topoisomerase II (TOP2) as one of the important regulators of the transcriptional activation of IEGs. However, the mechanism underlying transcriptional regulation involving TOP2 in IEG activation has remained unknown. Here, we demonstrate that ERK2, but not ERK1, is important for IEG transcriptional activation and report a critical ELK1 binding sequence for ERK2 function at the EGR1 gene. Our data indicate that both ERK1 and ERK2 extensively phosphorylate the C-terminal domain of TOP2B at mutual and distinctive residues. Although both ERK1 and ERK2 enhance the catalytic rate of TOP2B required to relax positive DNA supercoiling, ERK2 delays TOP2B catalysis of negative DNA supercoiling. In addition, ERK1 may relax DNA supercoiling by itself. ERK2 catalytic inhibition or knock-down interferes with transcription and deregulates TOP2B in IEGs. Furthermore, we present the first cryo-EM structure of the human cell-purified TOP2B and etoposide together with the EGR1 transcriptional start site (–30 to +20) that has the strongest affinity to TOP2B within –423 to +332. The structure shows TOP2B-mediated breakage and dramatic bending of the DNA. Transcription is activated by etoposide, while it is inhibited by ICRF193 at EGR1 and FOS, suggesting that TOP2B-mediated DNA break to favor transcriptional activation. Taken together, this study suggests that activated ERK2 phosphorylates TOP2B to regulate TOP2-DNA interactions and favor transcriptional activation in IEGs. We propose that TOP2B association, catalysis, and dissociation on its substrate DNA are important processes for regulating transcription and that ERK2-mediated TOP2B phosphorylation may be key for the catalysis and dissociation steps. Topoisomerase II (TOP2) has been identified as one of the regulators for the transcriptional activation of immediate early genes IEGs. Here the authors report that ERK1 and ERK2 oppositely regulate transcription and ERK2 regulates TOP2B-DNA interaction and catalysis to favor IEG transcription. [ABSTRACT FROM AUTHOR]

Mesoporous silica particles (MSPs) and polyethylene (PE) embedded films were prepared for better performance in extending the shelf life of products by improving the oxygen transmission rate (OTR) and the water vapor transmission rate (WVTR). The OTR and WVTR of the MSPs–PE film containing 3.65% MSPs were 13,293 cc/(m2 day) and 23.51 g/(m2 day), respectively, and showed 137% and 145% improvement compared to the PE film. In the evaluation of the freshness of bananas and strawberries using MSPs–PE film for 12 or 15 days, the change of Hunter's L* value of bananas and hardness of strawberries were preferred over the PE film. [ABSTRACT FROM AUTHOR]

The maintenance of lysosomal integrity is essential for lysosome function and cell fate. Damaged lysosomes are degraded by lysosomal autophagy, lysophagy. The mechanism underlying lysophagy remains largely unknown; this study aimed to contribute to the understanding of this topic. A cell-based screening system was used to identify novel lysophagy modulators. Triamterene (6-phenylpteridine-2,4,7-triamine) was identified as one of the most potent lysophagy inducers from the screening process. We found that triamterene causes lysosomal rupture without affecting other cellular organelles and increases autophagy flux in HepG2 cells. Damaged lysosomes in triamterene-treated cells were removed by autophagy-mediated pathway, which was inhibited by depletion of the autophagy regulator, ATG5 or SQSTM1. In addition, treatment of triamterene decreased the integrity of lysosome and cell viability, which were rescued by removing the triamterene treatment in HepG2 cells. Hence, our data suggest that triamterene is a novel lysophagy inducer through the disruption of lysosomal integrity. [ABSTRACT FROM AUTHOR]

In spore forming microbes, germination protease (GPR) plays a key role in the initiation of the germination process. A critical step during germination is the degradation of small acid-soluble proteins (SASPs), which protect spore DNA from external stresses (UV, heat, low temperature, etc.). Inactive zymogen GPR can be activated by autoprocessing of the N-terminal pro-sequence domain. Activated GPR initiates the degradation of SASPs; however, the detailed mechanisms underlying the activation, catalysis, regulation, and substrate recognition of GPR remain elusive. In this study, we determined the crystal structure of GPR from Paenisporosarcina sp. TG-20 (PaGPR) in its inactive form at a resolution of 2.5 A. Structural analysis showed that the active site of PaGPR is sterically occluded by an inhibitory loop region (residues 202–216). The N-terminal region interacts directly with the self-inhibitory loop region, suggesting that the removal of the N-terminal pro-sequence induces conformational changes, which lead to the release of the self-inhibitory loop region from the active site. In addition, comparative sequence and structural analyses revealed that PaGPR contains two highly conserved Asp residues (D123 and D182) in the active site, similar to the putative aspartic acid protease GPR from Bacillus megaterium. The catalytic domain structure of PaGPR also shares similarities with the sequentially non-homologous proteins HycI and HybD. HycI and HybD are metal-loproteases that also contain two Asp (or Glu) residues in their active site, playing a role in metal binding. In summary, our results provide useful insights into the activation process of PaGPR and its active conformation. [ABSTRACT FROM AUTHOR]

Fabricating composite films by dispersing clay in a polymer can provide functionalities such as antibiotic action and chemical adsorption. In this study, the effects of the shape and surface treatment of clay on the gas barrier properties, mechanical properties, thermal properties, and processing characteristics of polymer/clay composite films were investigated. Halloysites (HNTs) and vermiculites (VMTs), which are popular clays of the nanotube and nanoplate types, respectively, that are often employed to achieve functionality as they facilitate the carrying of chemicals, were incorporated into low-density polyethylene (LDPE). The effects of chemical treatment of the clay surface on the dispersibility of the clays in the polymer composites and on their properties were examined. Furthermore, the effects of the shapes and surface treatment of the clays on the drawabilities of the composite films, as well as the mechanical properties of the composite films according to the draw ratio were investigated. In the manufactured LDPE/clay composite films, the HNTs showed better dispersibility than the VMTs. After surface treatment with hydrochloric acid, the dispersibility improved relative to that before chemical treatment. With increasing clay content, the initial moduli of the composite sheets improved, but the tensile strengths and strains decreased. When VMTs were used, the gas barrier property of the composite film improved as the clay content increased; however, when HNTs were used, the gas barrier property decreased with increasing clay content When the clay surface was chemically treated, the drawabilities of the LDPE composites improved compared to those prior to surface treatment, and the drawabilities of the HNT composites were greater than those of the VMT composite. The maximum draw ratio of the surface-treated HNT composite film was the highest at 4.0, and the tensile strength increased by up to ≈3 times compared to that of the undrawn film. As the draw ratio increased, the gas barrier property, crystallinity, and the degree of orientation also increased. [ABSTRACT FROM AUTHOR]

Recent studies showed that Rai1 is a crucial component of the mRNA 5?-end-capping quality-control mechanism in yeast. The yeast genome encodes a weak homolog of Rai1, Ydr370C, but little is known about this protein. Here we report the crystal structures of Ydr370C from Kluyveromyces lactis and the first biochemical and functional studies on this protein. The overall structure of Ydr370C is similar to Rai1. Ydr370C has robust decapping activity on RNAs with unmethylated caps, but it has no detectable pyrophosphohydrolase activity. Unexpectedly, Ydr370C also possesses distributive, 5?-3? exoRNase activity, and we propose the name Dxo1 for this new eukaryotic enzyme with both decapping and exonuclease activities. Studies of yeast in which both Dxo1 and Rai1 are disrupted reveal that mRNAs with incomplete caps are produced even under normal growth conditions, in sharp contrast to current understanding of the capping process. [ABSTRACT FROM AUTHOR]

Exposure to fine particulate matter (PM) with diameter <2.5 µm (PM2.5) causes epithelium injury and endothelial dysfunction. Primary cilia are sensory organelles that transmit extracellular signals into intracellular biochemical responses and have roles in physiology. To date, there have been no studies investigating whether PM2.5 affects primary cilia in skin. We addressed this in the present study using normal human epidermal keratinocytes (NHEKs) and retinal pigment epithelium (RPE) cells. We found that formation of primary cilium is increased in differentiated NHEKs. However, treatment with PM2.5 blocked increased ciliogenesis in NHEKs and RPE cells. Furthermore, PM2.5 transcriptionally upregulated small proline rich protein 3 (SPRR3) expression by activating c-Jun, and ectopic expression of SPRR3 inhibits suppressed the ciliogenesis. Accordingly, treatment with c-Jun activator (anisomycin) induced SPRR3 expression, whereas the inhibitor (SP600125) recovered the ciliated cells and cilium length in PM2.5-treated cells. Moreover, c-Jun inhibitor suppressed upregulation of SPRR3 in PM2.5-treated cells. Taken together, our finding suggested that PM2.5 inhibits ciliogenesis by increasing SPRR3 expression via c-Jun activation in RPE cells and keratinocytes. [ABSTRACT FROM AUTHOR]