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FACT caught in the act of manipulating the nucleosome 期刊论文
NATURE, 2020, 577 (7790) : 426-+
作者:  Shen, Helen
收藏  |  浏览/下载:14/0  |  提交时间:2020/07/03

The organization of genomic DNA into nucleosomes profoundly affects all DNA-related processes in eukaryotes. The histone chaperone known as '  facilitates chromatin transcription'  (FACT(1)) (consisting of subunits SPT16 and SSRP1) promotes both disassembly and reassembly of nucleosomes during gene transcription, DNA replication and DNA repair(2). However, the mechanism by which FACT causes these opposing outcomes is unknown. Here we report two cryo-electron-microscopic structures of human FACT in complex with partially assembled subnucleosomes, with supporting biochemical and hydrogen-deuterium exchange data. We find that FACT is engaged in extensive interactions with nucleosomal DNA and all histone variants. The large DNA-binding surface on FACT appears to be protected by the carboxy-terminal domains of both of its subunits, and this inhibition is released by interaction with H2A-H2B, allowing FACT-H2A-H2B to dock onto a complex containing DNA and histones H3 and H4 (ref. (3)). SPT16 binds nucleosomal DNA and tethers H2A-H2B through its carboxy-terminal domain by acting as a placeholder for DNA. SSRP1 also contributes to DNA binding, and can assume two conformations, depending on whether a second H2A-H2B dimer is present. Our data suggest a compelling mechanism for how FACT maintains chromatin integrity during polymerase passage, by facilitating removal of the H2A-H2B dimer, stabilizing intermediate subnucleosomal states and promoting nucleosome reassembly. Our findings reconcile discrepancies regarding the many roles of FACT and underscore the dynamic interactions between histone chaperones and nucleosomes.


  
Universal quantum logic in hot silicon qubits 期刊论文
NATURE, 2020, 580 (7803) : 355-+
作者:  Li, Jia;  Yang, Xiangdong;  Liu, Yang;  Huang, Bolong;  Wu, Ruixia;  Zhang, Zhengwei;  Zhao, Bei;  Ma, Huifang;  Dang, Weiqi;  Wei, Zheng;  Wang, Kai;  Lin, Zhaoyang;  Yan, Xingxu;  Sun, Mingzi;  Li, Bo;  Pan, Xiaoqing;  Luo, Jun;  Zhang, Guangyu;  Liu, Yuan;  Huang, Yu;  Duan, Xidong;  Duan, Xiangfeng
收藏  |  浏览/下载:62/0  |  提交时间:2020/07/03

Quantum computation requires many qubits that can be coherently controlled and coupled to each other(1). Qubits that are defined using lithographic techniques have been suggested to enable the development of scalable quantum systems because they can be implemented using semiconductor fabrication technology(2-5). However, leading solid-state approaches function only at temperatures below 100 millikelvin, where cooling power is extremely limited, and this severely affects the prospects of practical quantum computation. Recent studies of electron spins in silicon have made progress towards a platform that can be operated at higher temperatures by demonstrating long spin lifetimes(6), gate-based spin readout(7) and coherent single-spin control(8). However, a high-temperature two-qubit logic gate has not yet been demonstrated. Here we show that silicon quantum dots can have sufficient thermal robustness to enable the execution of a universal gate set at temperatures greater than one kelvin. We obtain single-qubit control via electron spin resonance and readout using Pauli spin blockade. In addition, we show individual coherent control of two qubits and measure single-qubit fidelities of up to 99.3 per cent. We demonstrate the tunability of the exchange interaction between the two spins from 0.5 to 18 megahertz and use it to execute coherent two-qubit controlled rotations. The demonstration of '  hot'  and universal quantum logic in a semiconductor platform paves the way for quantum integrated circuits that host both the quantum hardware and its control circuitry on the same chip, providing a scalable approach towards practical quantum information processing.


  
Fine Sediment Deposition and Filtration Under Losing and Gaining Flow Conditions: A Particle Tracking Model Approach 期刊论文
WATER RESOURCES RESEARCH, 2020, 56 (2)
作者:  Preziosi-Ribero, Antonio;  Packman, Aaron I.;  Escobar-Vargas, Jorge A.;  Phillips, Colin B.;  Donado, Leonardo David;  Arnon, Shai
收藏  |  浏览/下载:29/0  |  提交时间:2020/07/02
sediment deposition  groundwater surface water interaction  hyporheic exchange  particle tracking  
Kilometer-Scale Hydrologic Exchange Flows in a Gravel Bed River Corridor and Their Implications to Solute Migration 期刊论文
WATER RESOURCES RESEARCH, 2020, 56 (2)
作者:  Zachara, John M.;  Chen, Xingyuan;  Song, Xuehang;  Shuai, Pin;  Murray, Chris;  Resch, C. Tom
收藏  |  浏览/下载:22/0  |  提交时间:2020/07/02
surface water-groundwater interaction  gravel bed river corridor  hydrologic exchange  subsurface hydrogeologic structures  riverine and groundwater modeling  contaminant plume dynamics  
Using 4-km WRF CONUS simulations to assess impacts of the surface coupling strength on regional climate simulation 期刊论文
CLIMATE DYNAMICS, 2019, 53: 6397-6416
作者:  Chen, Liang;  Li, Yanping;  Chen, Fei;  Barlage, Michael;  Zhang, Zhe;  Li, Zhenhua
收藏  |  浏览/下载:18/0  |  提交时间:2019/11/27
Surface exchange coefficient  Surface coupling strength  Surface fluxes  Land-atmosphere interaction  
Radiation and energy balance dynamics over a rapidly receding glacier in the central Himalaya 期刊论文
INTERNATIONAL JOURNAL OF CLIMATOLOGY, 2019
作者:  Singh, Nilendu;  Singhal, Mohit;  Chhikara, Sudershan;  Karakoti, Indira;  Chauhan, Pankaj;  Dobhal, Dwarika P.
收藏  |  浏览/下载:26/0  |  提交时间:2019/11/27
central Himalaya  energy-water exchange  glacier-atmosphere interaction  hydrometeorology  melt energy  summer-accumulation-type glacier  surface fluxes  
Water Mass Analysis and End-Member Mixing Contribution Using Coupled Radiogenic Nd Isotopes and Nd Concentrations: Interaction Between Marginal Seas and the Northwestern Pacific 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2018, 45 (5) : 2388-2395
作者:  Che, Hong;  Zhang, Jing
收藏  |  浏览/下载:7/0  |  提交时间:2019/04/09
Nd isotope  water mass  interaction exchange  northwestern Pacific  marginal seas