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首页> 外文期刊>Nucleus >Chromosomes without a 30-nm chromatin fiber.
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Chromosomes without a 30-nm chromatin fiber.

机译：没有30 nm染色质纤维的染色体。

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摘要

How is a long strand of genomic DNA packaged into a mitotic chromosome or nucleus? The nucleosome fiber (beads-on-a-string), in which DNA is wrapped around core histones, has long been assumed to be folded into a 30-nm chromatin fiber, and a further helically folded larger fiber. However, when frozen hydrated human mitotic cells were observed using cryoelectron microscopy, no higher-order structures that included 30-nm chromatin fibers were found. To investigate the bulk structure of mitotic chromosomes further, we performed small-angle X-ray scattering (SAXS), which can detect periodic structures in noncrystalline materials in solution. The results were striking: no structural feature larger than 11 nm was detected, even at a chromosome-diameter scale (~1 μm). We also found a similar scattering pattern in interphase nuclei of HeLa cells in the range up to ~275 nm. Our findings suggest a common structural feature in interphase and mitotic chromatins: compact and irregular folding of nucleosome fibers occurs without a 30-nm chromatin structure.
机译：基因组DNA的长链如何包装到有丝分裂的染色体或核中？长期以来，人们一直认为将核糖体纤维（串珠）包裹在核心组蛋白周围，然后将其折叠成30 nm的染色质纤维，再将其螺旋折叠成较大的纤维。但是，当使用冷冻电子显微镜观察到冷冻的水合人类有丝分裂细胞时，没有发现包含30 nm染色质纤维的高阶结构。为了进一步研究有丝分裂染色体的整体结构，我们进行了小角度X射线散射（SAXS），可以检测溶液中非晶态材料的周期性结构。结果令人震惊：即使在染色体直径范围（〜1μm）下也未检测到大于11 nm的结构特征。我们还在HeLa细胞的相间核中发现了相似的散射模式，范围高达275 nm。我们的研究结果表明相间和有丝分裂染色质的共同结构特征：核小体纤维的紧凑和不规则折叠发生而没有30 nm染色质结构。

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