20 research outputs found
Binding of guide piRNA triggers methylation of the unstructured N-terminal region of Aub leading to assembly of the piRNA amplification complex
Piwi proteins use guide piRNAs to repress selfish genomic elements, protecting the genomic integrity of gametes and ensuring the fertility of animal species. Efficient transposon repression depends on amplification of piRNA guides in the ping-pong cycle, which in Drosophila entails tight cooperation between two Piwi proteins, Aub and Ago3. Here we show that post-translational modification, symmetric dimethylarginine (sDMA), of Aub is essential for piRNA biogenesis, transposon silencing and fertility. Methylation is triggered by loading of a piRNA guide into Aub, which exposes its unstructured N-terminal region to the PRMT5 methylosome complex. Thus, sDMA modification is a signal that Aub is loaded with piRNA guide. Amplification of piRNA in the ping-pong cycle requires assembly of a tertiary complex scaffolded by Krimper, which simultaneously binds the N-terminal regions of Aub and Ago3. To promote generation of new piRNA, Krimp uses its two Tudor domains to bind Aub and Ago3 in opposite modification and piRNA-loading states. Our results reveal that post-translational modifications in unstructured regions of Piwi proteins and their binding by Tudor domains that are capable of discriminating between modification states is essential for piRNA biogenesis and silencing
Binding of guide piRNA triggers methylation of the unstructured N-terminal region of Aub leading to assembly of the piRNA amplification complex
Piwi proteins use guide piRNAs to repress selfish genomic elements, protecting the genomic integrity of gametes and ensuring the fertility of animal species. Efficient transposon repression depends on amplification of piRNA guides in the ping-pong cycle, which in Drosophila entails tight cooperation between two Piwi proteins, Aub and Ago3. Here we show that post-translational modification, symmetric dimethylarginine (sDMA), of Aub is essential for piRNA biogenesis, transposon silencing and fertility. Methylation is triggered by loading of a piRNA guide into Aub, which exposes its unstructured N-terminal region to the PRMT5 methylosome complex. Thus, sDMA modification is a signal that Aub is loaded with piRNA guide. Amplification of piRNA in the ping-pong cycle requires assembly of a tertiary complex scaffolded by Krimper, which simultaneously binds the N-terminal regions of Aub and Ago3. To promote generation of new piRNA, Krimp uses its two Tudor domains to bind Aub and Ago3 in opposite modification and piRNA-loading states. Our results reveal that post-translational modifications in unstructured regions of Piwi proteins and their binding by Tudor domains that are capable of discriminating between modification states is essential for piRNA biogenesis and silencing
Generation of Hierarchically Ordered Structures on a Polymer Film by Electrohydrodynamic Structure Formation
Rectangle-capped and tilted micropillar array for enhanced anisotropic anti-shearing in biomimetic adhesion
The Role of EGFR/PI3K/Akt/cyclinD1 Signaling Pathway in Acquired Middle Ear Cholesteatoma
Cholesteatoma is a benign keratinizing and hyper proliferative squamous epithelial lesion of the temporal bone. Epidermal growth factor (EGF) is one of the most important cytokines which has been shown to play a critical role in cholesteatoma. In this investigation, we studied the effects of EGF on the proliferation of keratinocytes and EGF-mediated signaling pathways underlying the pathogenesis of cholesteatoma. We examined the expressions of phosphorylated EGF receptor (p-EGFR), phosphorylated Akt (p-Akt), cyclinD1, and proliferating cell nuclear antigen (PCNA) in 40 cholesteatoma samples and 20 samples of normal external auditory canal (EAC) epithelium by immunohistochemical method. Furthermore, in vitro studies were performed to investigate EGF-induced downstream signaling pathways in primary external auditory canal keratinocytes (EACKs). The expressions of p-EGFR, p-Akt, cyclinD1, and PCNA in cholesteatoma epithelium were significantly increased when compared with those of control subjects. We also demonstrated that EGF led to the activation of the EGFR/PI3K/Akt/cyclinD1 signaling pathway, which played a critical role in EGF-induced cell proliferation and cell cycle progression of EACKs. Both EGFR inhibitor AG1478 and PI3K inhibitor wortmannin inhibited the EGF-induced EGFR/PI3K/Akt/cyclinD1 signaling pathway concomitantly with inhibition of cell proliferation and cell cycle progression of EACKs. Taken together, our data suggest that the EGFR/PI3K/Akt/cyclinD1 signaling pathway is active in cholesteatoma and may play a crucial role in cholesteatoma epithelial hyper-proliferation. This study will facilitate the development of potential therapeutic targets for intratympanic drug therapy for cholesteatoma
Discretely Supported Dry Adhesive Film Inspired by Biological Bending Behavior for Enhanced Performance on a Rough Surface
Biologically
inspired dry adhesion has recently become a research hot topic because
of its practical significance in scientific research and instrumental
technology. Yet, most of the current studies merely focus on borrowing
the concept from some finer biological contact elements but lose sight
of the foundation ones that play an equally important role in the
adhesion functionality. Inspired by the bending behavior of the flexible
foundation element of a gecko (lamellar skin) in attachment motion,
in this study, a new type of dry adhesive structure was proposed,
wherein a mushroom-shaped micropillar array behaving as a strongly
adhesive layer was engineered on a discretely supported thin film.
We experimentally observed and analytically modeled the structural
deformation and found that the energy penalty could be largely reduced
because of the partial shift from pillar bending to film bending.
Such behavior is very analogous in functionality to the lamellar skin
in a gecko’s pads and is helpful in effectively limiting the
damage of the contact interface, thus generating enhanced adhesion
even on a rough surface
Structure of the Arabidopsis JMJ14-H3K4me3 Complex Provides Insight into the Substrate Specificity of KDM5 Subfamily Histone Demethylases
Discretely Supported Dry Adhesive Film Inspired by Biological Bending Behavior for Enhanced Performance on a Rough Surface
Biologically
inspired dry adhesion has recently become a research hot topic because
of its practical significance in scientific research and instrumental
technology. Yet, most of the current studies merely focus on borrowing
the concept from some finer biological contact elements but lose sight
of the foundation ones that play an equally important role in the
adhesion functionality. Inspired by the bending behavior of the flexible
foundation element of a gecko (lamellar skin) in attachment motion,
in this study, a new type of dry adhesive structure was proposed,
wherein a mushroom-shaped micropillar array behaving as a strongly
adhesive layer was engineered on a discretely supported thin film.
We experimentally observed and analytically modeled the structural
deformation and found that the energy penalty could be largely reduced
because of the partial shift from pillar bending to film bending.
Such behavior is very analogous in functionality to the lamellar skin
in a gecko’s pads and is helpful in effectively limiting the
damage of the contact interface, thus generating enhanced adhesion
even on a rough surface