发表在BioMed Central开放期刊Cell & Bioscience 上的新研究，首次说明了左旋型的Z型DNA，它通常只被发现于DNA被复制的地方，也能在核小体上形成。
提供生命蓝图的DNA结构曾被描述为一个双螺旋。为了节省细胞核内空间，DNA紧紧地缠绕形成核小体的蛋白质，然后进一步缠绕，压缩成染色质，接着压缩成染色体。但是，右手螺旋（也称为B型DNA）的这种熟悉形象不是DNA的唯一形式。在DNA被复制成RNA的位置（用作制造蛋白质指令的信使），DNA需要解缠绕，在负超螺旋过程中，能形成DNA双螺旋的左手螺旋变体（Z-DNA）。
最开始认为，Z-DNA只能在活性RNA聚合酶（组装RNA的酶）存在下形成。但是，最近发现，SWI/SNF能将某些B-DNA序列转换成Z-DNA，其中SWI/SNF是一种参与重塑核小体和允许RNA聚合酶接近DNA的蛋白质。
由Keji Zhao博士领导的研究小组发现，他们通过增加SWI/SNF 和 ATP（细胞能量来源）能将核小体上的B-DNA转换成Z-DNA，形成的Z-核小体是一种新结构。
来自美国国立卫生研究院的赵博士解释说，"事实上，我们在核小体上发现Z-DNA的事实是理解染色体重组与Z-DNA调节基因表达的作用的新一步。然而，Z-核小体很可能是一个暂时结构，但它为DNA结合蛋白配置提供了一个机会的窗口，这可以招募、调节或阻止转录机制和蛋白表达。"（生物谷bioon.com）
doi:10.1186/2045-3701-2-3
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SWI/SNF-mediated chromatin remodeling induces Z-DNA formation on a nucleosome
Niveen Mulholland, Yan Xu, Hiroshi Sugiyama, Keji Zhao
Abstract Background Z-DNA is a higher-energy, left-handed form of the double helix. A primary function of Z-DNA formation is to facilitate transcriptional initiation and activation. Sequences favoring Z-DNA formation are frequently located in promoter regions and Z-DNA is stabilized by torsional strain resulting from negative supercoiling, such as that generated by an actively transcribing polymerase or by a nucleosome remodeling event. We previously have shown that activation of the CSF1 gene by a chromatin remodeling event in the promoter results in Z-DNA formation at TG repeats within the promoter. Results We show that remodeling of a mononucleosome by the human SWI/SNF complex results in Z-DNA formation when the DNA within the mononucleosome contains Z-DNA favoring sequence. Nuclease accessibility patterns of nucleosome core particle consisting of Z-DNA are quite different from counterpart nucleosomes containing classic B-DNA. Z-nucleosomes represent a novel mononucleosome structure. Conclusions: We present evidence that Z-DNA can form on nucleosomes though previous observations indicate the occlusion of nucleosome formation from Z-DNA.
