發(fā)表在BioMed Central開放期刊Cell & Bioscience 上的新研究,，首次說明了左旋型的Z型DNA,，它通常只被發(fā)現(xiàn)于DNA被復(fù)制的地方，也能在核小體上形成,。
提供生命藍(lán)圖的DNA結(jié)構(gòu)曾被描述為一個(gè)雙螺旋,。為了節(jié)省細(xì)胞核內(nèi)空間，DNA緊緊地纏繞形成核小體的蛋白質(zhì),，然后進(jìn)一步纏繞,，壓縮成染色質(zhì)，接著壓縮成染色體。但是,，右手螺旋（也稱為B型DNA）的這種熟悉形象不是DNA的唯一形式,。在DNA被復(fù)制成RNA的位置（用作制造蛋白質(zhì)指令的信使），DNA需要解纏繞,，在負(fù)超螺旋過程中,，能形成DNA雙螺旋的左手螺旋變體（Z-DNA）。
最開始認(rèn)為,，Z-DNA只能在活性RNA聚合酶（組裝RNA的酶）存在下形成,。但是,，最近發(fā)現(xiàn),，SWI/SNF能將某些B-DNA序列轉(zhuǎn)換成Z-DNA，其中SWI/SNF是一種參與重塑核小體和允許RNA聚合酶接近DNA的蛋白質(zhì),。
由Keji Zhao博士領(lǐng)導(dǎo)的研究小組發(fā)現(xiàn),，他們通過增加SWI/SNF 和 ATP（細(xì)胞能量來源）能將核小體上的B-DNA轉(zhuǎn)換成Z-DNA，形成的Z-核小體是一種新結(jié)構(gòu),。
來自美國國立衛(wèi)生研究院的趙博士解釋說,，"事實(shí)上，我們在核小體上發(fā)現(xiàn)Z-DNA的事實(shí)是理解染色體重組與Z-DNA調(diào)節(jié)基因表達(dá)的作用的新一步,。然而,，Z-核小體很可能是一個(gè)暫時(shí)結(jié)構(gòu)，但它為DNA結(jié)合蛋白配置提供了一個(gè)機(jī)會的窗口,，這可以招募,、調(diào)節(jié)或阻止轉(zhuǎn)錄機(jī)制和蛋白表達(dá)。"（生物谷bioon.com）
doi:10.1186/2045-3701-2-3
PMC:
PMID:
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.
