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Nsi1 plays a significant role in the silencing of ribosomal DNA in <i>Saccharomyces cerevisiae</i>
Ha, Cheol Woong,Sung, Min-Kyung,Huh, Won-Ki Oxford University Press 2012 Nucleic acids research Vol.40 No.11
<P>In eukaryotic cells, ribosomal DNA (rDNA) forms the basis of the nucleolus. In <I>Saccharomyces cerevisiae</I>, 100–200 copies of a 9.1-kb rDNA repeat exist as a tandem array on chromosome XII. The stability of this highly repetitive array is maintained through silencing. However, the precise mechanisms that regulate rDNA silencing are poorly understood. Here, we report that <I>S. cerevisiae</I> Ydr026c, which we name NTS1 silencing protein 1 (Nsi1), plays a significant role in rDNA silencing. By studying the subcellular localization of 159 nucleolar proteins, we identified 11 proteins whose localization pattern is similar to that of Net1, a well-established rDNA silencing factor. Among these proteins is Nsi1, which is associated with the NTS1 region of rDNA and is required for rDNA silencing at NTS1. In addition, Nsi1 physically interacts with the known rDNA silencing factors Net1, Sir2 and Fob1. The loss of Nsi1 decreases the association of Sir2 with NTS1 and increases histone acetylation at NTS1. Furthermore, Nsi1 contributes to the longevity of yeast cells. Taken together, our findings suggest that Nsi1 is a new rDNA silencing factor that contributes to rDNA stability and lifespan extension in <I>S. cerevisiae</I>.</P>
Ha, Cheol Woong,Huh, Won-Ki Oxford University Press 2011 Nucleic acids research Vol.39 No.4
<P>The target of rapamycin (TOR) kinase is an evolutionarily conserved key regulator of eukaryotic cell growth and proliferation. Recently, it has been reported that inhibition of TOR signaling pathway can delay aging and extend lifespan in several eukaryotic organisms, but how lifespan extension is mediated by inhibition of TOR signaling is poorly understood. Here we report that rapamycin treatment and nitrogen starvation, both of which cause inactivation of TOR complex 1 (TORC1), lead to enhanced association of Sir2 with ribosomal DNA (rDNA) in <I>Saccharomyces cerevisiae</I>. TORC1 inhibition increases transcriptional silencing of RNA polymerase II-transcribed gene integrated at the rDNA locus and reduces homologous recombination between rDNA repeats that causes formation of toxic extrachromosomal rDNA circles. In addition, TORC1 inhibition induces deacetylation of histones at rDNA. We also found that Pnc1 and Net1 are required for enhancement of association of Sir2 with rDNA under TORC1 inhibition. Taken together, our findings suggest that inhibition of TORC1 signaling stabilizes the rDNA locus by enhancing association of Sir2 with rDNA, thereby leading to extension of replicative lifespan in <I>S. cerevisiae</I>.</P>
극저온 실험 및 해석 기반 LNG 운반선 용 강화 폴리우레탄의 기계적 특성 평가
장철웅(Cheol-Woong Jang),심천식(Chun-Sik Shim),송하철(Ha-Cheol Song),송창용(Chang Yong Song) 대한조선학회 2012 대한조선학회 학술대회자료집 Vol.2012 No.5
In the context of structural performance on LNG hold, the mechanical characteristics of insulation material are considered a critical design factor under a cryogenic temperature. This paper presents the thermo-elastic behavior of the reinforced polyurethane foam (RPUF) adapted for the insulation material of membrane type LNG carrier via both experiments and numerical simulations realizing the cryogenic condition. The experiments are carried out to investigate the characteristics for thermal transfer and static compressive deformation on the actual RPUF specimen. The heat transfer simulations based on finite element method (FEM) include forced convection analysis. The heat transfer results are mapped on structural analysis model to carry out thermal coupled analysis. Thermo-elastic behaviors estimated by simulations are compared to experimental results.
극저온 실험 및 해석 기반 LNG 운반선 용 강화 폴리우레탄의 기계적 특성 평가
장철웅(Cheol-Woong Jang),심천식(Chun-Sik Shim),송하철(Ha-Cheol Song),송창용(Chang Yong Song) 한국해양환경·에너지학회 2012 한국해양환경·에너지학회 학술대회논문집 Vol.2012 No.5
In the context of structural performance on LNG hold, the mechanical characteristics of insulation material are considered a critical design factor under a cryogenic temperature. This paper presents the themo-elastic behavior of the reinforced polyurethane foam (RPUF) adapted for the insulation material of membrane type LNG earner via both experiments and numerical simulations realizing the cryogenic condition. The experiments are carried out to investigate the characteristics for thermal transfer and static compressive deformation on the actual RPUF specimen. The heat transfer simulations based on finite element method (FEW include forced convection analysis. The heat transfer results are mapped on structural analysis model to carry out thermal coupled analysis. Thermo-elastic behaviors estimated by simulations are compared to experimental results.
멤브레인 LNG 선박용 강화 폴리우레탄폼의 극저온 거동 연구
장철웅(Cheol-Woong Jang),심천식(Chun-Sik Shim),송하철(Ha-Cheol Song),송창용(Chang Yong Song) 한국해양공학회 2013 韓國海洋工學會誌 Vol.27 No.1
In the context of the structural performance of an LNG hold, the mechanical characteristics of the insulation material are considered to be a critical design factor under cryogenic temperatures. This paper presents the thermal elasto-plastic behavior of the reinforced polyurethane foam(RPUF) adapted for the insulation material of a membrane type LNG carried via both experiments and numerical simulations realizing the cryogenic condition. The experiments are carried out to investigate the thermal transfer and thermal elasto-plastic deformation characteristics of an actual RPUE specimen. The heat transfer simulations based on the finite element method(FEM) include a forced convection analysis. The results of heat transfer analyses are compared with the experimental results. Reasonable cryogenic conditions for RPUF are reviewed based on both the analysis and experimental results.