Spontaneous DNA Lesions Modulate DNA Structural Transitions Occurring at Nuclease Hypersensitive Element III1 of the Human c-myc Proto-Oncogene
Spontaneous DNA Lesions Modulate DNA Structural Transitions Occurring at Nuclease Hypersensitive Element III1 of the Human c-myc Proto-Oncogene
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DOI：
10.1021/bi300304k
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发表时间：
2012-07-03
期刊：
影响因子：
2.9
通讯作者：
Tornaletti, Silvia
中科院分区：
文献类型：
--
作者：
Beckett, Joshua;Burns, Jacob;Tornaletti, Silvia
G四链体（G4）DNA是一种非典型的四链DNA结构，在钾离子存在下，可以通过堆叠称为G四联体的四个氢键鸟嘌呤的平面阵列形成G重复序列。除了在基因表达调控中的假定功能外，G4 DNA还定位于通常以基因组不稳定性为特征的区域。这表明这种结构的形成可能会干扰DNA的处理，包括这些位点的DNA损伤处理。在这里，我们研究了两个自发的DNA损伤，脱碱基位点和8-氧代鸟嘌呤，从双链体到四链体DNA结构的转变发生在核酸酶超敏元件III 1（NHEIII 1）的人c-myc启动子的效果。我们通过硫酸二甲酯足迹法和RNA聚合酶阻滞试验表明，在生理浓度的钾离子NHEIII 1折叠成两个共存的G4 DNA结构，myc-1245和myc-2345，这取决于G运行被用于G四联体形成。我们发现，用单个脱碱基位点或单个8-氧代鸟嘌呤对NHEIII 1的G12进行单次取代可阻止G4结构myc-2345的形成，而有利于结构myc-1245的形成，其中损伤被容纳在由G11-AP 12/（或8-oxoG 12）-G13-G14形成的DNA环中。令人惊讶的是，当在NHEIII 1的3位引入额外的G到A碱基取代时，我们观察到myc-2345的形成。这种结构转变的程度由G11-G14重复内病变的位置和类型调制。我们的数据表明，自发病变形成的G4-形成序列的c-myc NHEIII 1的影响发生在这个监管网站的结构转换，可能改变转录因子结合和DNA修复病变形成在这个高度调节的序列。
G quadruplex (G4) DNA is a noncanonical four-stranded DNA structure that can form in G repeats by stacking of planar arrays of four hydrogen-bonded guanines called G quartets, in the presence of potassium ions. In addition to a presumed function in the regulation of gene expression, G4 DNA also localizes to regions often characterized by genomic instability. This suggests that formation of this structure may interfere with DNA transactions, including processing of DNA damage at these sites. Here we have studied the effect of two spontaneous DNA lesions, the abasic site and 8-oxoguanine, on the transition from duplex to quadruplex DNA structure occurring at nuclease hypersensitive element III1 (NHEIII1) of the human c-myc promoter. We show by dimethyl sulfate footprinting and RNA polymerase arrest assays that at physiological concentrations of potassium ions NHEIII1 folds into two coexisting G4 DNA structures, myc-1245 and myc-2345, depending on which G runs are utilized for G quartet formation. We found that a single substitution of G12 of NHEIII1 with a single abasic site or a single 8-oxoguanine prevented formation of G4 structure myc-2345 in favor of structure myc-1245, where the lesion was accommodated in a DNA loop formed by G11-AP12/(or 8-oxoG12)-G13-G14. Surprisingly, when an additional G to A base substitution was introduced at position 3 of NHEIII1, we observed formation of myc-2345. The extent of this structural transition was modulated by the location and type of lesion within the G11-G14 repeat. Our data indicate that spontaneous lesions formed in the G4-forming sequence of c-myc NHEIII1 affect the structural transitions occurring at this regulatory site, potentially altering transcription factor binding and DNA repair of lesions formed in this highly regulated sequence.