Counterion-mediated decompaction of liquid crystalline chromosomes.
Counterion-mediated decompaction of liquid crystalline chromosomes.
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DOI：
10.1089/dna.2012.1708
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发表时间：
2012-11
影响因子：
3.1
通讯作者：
Shiyong Sun;J. Wong;Mingxue Liu;F. Dong
中科院分区：
文献类型：
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作者：
Shiyong Sun;J. Wong;Mingxue Liu;F. Dong
DNA 和核小体核心颗粒的液晶相可以在体外形成，表明这些相在体内基因组的维持和压缩中发挥着至关重要的作用。在本研究中，在高度纯化的蝶形凯伦藻细胞核中鉴定出连续水平的液晶解压缩，以响应乙二胺四乙酸（EDTA）对二价抗衡离子的逐渐螯合；使用偏光显微镜、共焦激光扫描显微镜和透射电子显微镜观察到解压缩，并利用微量热法进一步证实。在染色体解压缩的早期阶段，观察到染色质 150 nm 弧形带中的嵌套纤维卷。孤立核的微量热谱揭示了核解压缩的动态过程以非线性方式发生；此外，还发现了 60°C-70°C 之间的 EDTA 敏感热转变，对应于染色体的液晶相变。结果表明，纤维状染色质丝的嵌套卷曲负责甲藻染色体液晶和双折射特征的建立和稳定。结果还表明，带正电荷的二价抗衡离子在调节液晶相以压缩甲藻染色体方面发挥着重要作用。
Liquid crystalline phases of DNA and nucleosome core particles can be formed in vitro, indicating the crucial roles of these phases in the maintenance and compaction of genomes in vivo. In the present study, sequential levels of liquid crystalline decompaction were identified in highly purified nuclei of Karenia papilionacea in response to the gradual chelation of divalent counterions by ethylenediaminetetraacetic acid (EDTA); the decompaction was observed using polarizing light microscopy, confocal laser scanning microscopy, and transmission electron microscopy and further confirmed utilizing microcalorimetry. Nested fibrous coils in 150 nm arc-like bands of chromatin were observed in the early stages of chromosomal decompaction. The microcalorimetry spectra of isolated nuclei revealed that the dynamic processes of nuclear decompaction occurred in a nonlinear manner; in addition, an EDTA-sensitive thermal transition between 60°C-70°C, corresponding to a liquid-crystalline-phase transition of chromosomes, was found. The results suggested that nested coils of fibrous chromatin filaments are responsible for the establishment and stabilization of the liquid crystalline and birefringence features of the chromosomes of dinoflagellates. The results also indicated that positively charged divalent counterions play significant roles in modulating liquid crystalline phases to compact the chromosomes of dinoflagellates.