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A Pumilio Activity Sensor Reveals Bagof- Marbles Inhibition of Pum Activity in the Drosophila Ovary
장위정,김창수 한국발생생물학회 2023 발생과 생식 Vol.27 No.1
Pumilio (Pum) is an RNA-binding protein and translational repressor important to diverse biological processes. In the Drosophila ovary, Pum is expressed in female germline stem cells (GSCs), wherein it acts as an intrinsic stem cell maintenance factor via repressing target mRNAs that are as yet mostly unknown. Pum recognizes the Pum binding sequence (PBS) in the mRNA 3’UTR through its C-terminus Puf domain. Translational repression is mediated through its N-terminal domain, but the molecular mechanism remains largely unknown. We previously showed that Bag-of-marbles, a critical differentiation-promoting factor of female GSCs, physically interacts with the N-terminus of Pum. We further showed that this interaction is critical to Bam inhibition of Pum repressive action in cultured cells, but the physiological relevance was not addressed. Here we design an in vivo GFP translational reporter bearing the PBS in its 3’UTR and show that GFP expression is reduced in cells wherein Pum is known to be active. Furthermore, we demonstrate in pum mutant ovary that this GFP repression requires Pum, and also that the sensor faithfully monitors Pum activity. Finally, we show that forced expression of Bam inhibits Pum-mediated repression, validating that Bam inhibits Pum activity in vivo.
Channel-Free Control of Eutectic Gallium-Indium Droplets by Magnetically Active Microwall Arrays
장새봄,박정은,전지수,위정재 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.2
Eutectic Gallium-Indium (EGaIn) is quickly emerging as wirelessly controlled conducting material for alternatives to mercury since it remains in a liquid state at room temperature without toxicity. In this presentation, we suggest a novel method to spatially control EGaIn droplet by contactless magnetic actuation of magnetically responsive microwall arrays. The microwalls consisted with polydimethylsiloxane (PDMS) and iron particles have a large aspect ratio (>7). Since the bottom part of the microwall is fixed by magnetically inert neat PDMS substrate, the top part of the microwall bends upon response to an external magnetic field. To implement effective EGaIn droplet transportation, we will discuss various parameter studies related to the bending actuation of microwall arrays throughout iterative bending cycles. Furthermore, merger of two EGaIn droplets was demonstrated by managing transportation direction of the droplets.
장새봄,조웅비,이서구,유아란,위정재 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
Microcrystalline cellulose (MCC) is biodegradable polymer with high crystallinity. Many researchers investigated polymer-MCC composites owing to lightweight yet high mechanical property of MCC. High mechanical property of MCC, however, originates from strong intermolecular hydrogen bonding of hydroxyl groups, which can lead to aggregation-induced reduction in interfacial areas and mechanical properties in polymer composites. To alleviate the MCC aggregation in thermoplastic polyurethane (TPU) composites, hydroxyl groups in MCC are substituted by methyl or hydroxypropyl groups. Although the modified MCC (m-MCC) has higher compatibility than that of pristine MCC due to the decrease in hydrogen bonding among MCCs, m-MCC has lower crystallinity and mechanical properties. In this study, we will investigate the chemical modification effects of MCC on TPU/m-MCC composites with a detailed study on structure-property relationships.
이서구,조웅비,장새봄,유아란,위정재 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.2
Microcrystalline cellulose (MCC) has various advantages including high mechanical properties. However, too strong interactions among MCCs can lead to aggregation of the MCC fillers within polymer composites, which can reduce interfacial between polymer matrix and filler and reinforcement effects. Herein, we employed three different chemically modified MCC (m-MCC) where hydroxyl groups of the MCCs was substituted by either methyl or hydroxypropyl groups. The m-MCC and ester type thermoplastic polyurethane (TPU) were compounded by an extrusion process. As the chemical substitution of hydroxyl groups can reduce the number of hydrogen bonding sites or increase m-MCC intermolecular distances, both crystallinity of m-MCCs and polymer-filler interaction can also be manipulated. In this presentation, we will discuss structure-property relationships of TPU-MCC composites with focuses on correlation of crystallinity and dispersion of m-MCC with mechanical properties of the TPU-MCC composites.
Sumira Malik,장위정,김창수 한국발생생물학회 2017 발생과 생식 Vol.21 No.4
The germline stem cells of the Drosophila ovary continuously produce eggs throughout the life- span. Intricate regulation of stemness and differentiation is critical to this continuous production. The translational regulator Nos is an intrin-sic factor that is required for maintenance of stemness in germline stem cells. Nos expression is reduced in differentiating cells at the post-transcriptional level by diverse translational regulators. However, molecular mechanisms underlying Nos re-pression are not completely understood. Through three distinct protein-protein interaction experiments, we identified specific molecular interactions between translational regulators involved in Nos repression. Our findings suggest a model in which protein complexes assemble on the 3’ untranslated region of Nos mRNA in order to regulate Nos expression at the post-transcriptional level.
Lin28 and Imp are Required for Stability of Bowl Transcripts in Hub Cells of the Drosophila Testis
Van To,Hyun Ju Kim,장위정,Perinthottathil Sreejith,김창수 한국발생생물학회 2021 발생과 생식 Vol.25 No.4
Hub cells comprise a niche for germline stem cells and cyst stem cells in the Drosophila testis. Hub cells arise from common somatic gonadal precursors in embryos, but the mechanism of their specification is still poorly understood. Here we find that RNA binding proteins Lin28 and Imp mediate transcript stability of Bowl, a known hub specification factor; Bowl transcripts were reduced in the testis of Lin28 and Imp mutants, and also when RNAmediated interference against Lin28 or Imp was expressed in hub cells. In tissue culture Luciferase assays involving the Bowl 3’UTR, stability of Luc reporter transcripts depended on the Bowl 3’UTR and required Lin28 and Imp. Our findings suggest that proper Bowl function during hub cell specification requires Lin28 and Imp in the testis hub cells.