Two-quartet kit* G-quadruplex is formed via double-stranded pre-folded structure
Two-quartet kit* G-quadruplex is formed via double-stranded pre-folded structure
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DOI：
10.1093/nar/gky1269
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发表时间：
2019-03-18
影响因子：
14.9
通讯作者：
Plavec, Janez
中科院分区：
文献类型：
--
作者：
Kotar, Anita;Rigo, Riccardo;Plavec, Janez
在c-KIT原癌基因的启动子中，其失调与许多癌症有关，三个富含g的区域（kit1， kit*和kit2）能够折叠成g -四联体。虽然kit1和kit2已被深入研究，但关于kit*折叠行为的信息很少，尽管它在调节c-KIT转录中起关键作用。值得注意的是，试剂盒*包含SP1和AP2转录因子的共识位点。本文通过一组互补的光谱和生物物理方法发现，试剂盒*，d[GGCGAGGAGGGGCGTGGCCGGC]在生理相关浓度的KCl下，采用椅型反平行g -四联体，具有两个g -四联体。在Na+和NH4+离子存在的情况下，观察到结构的非均相系综，但它们稳定了预折叠结构。在K+离子存在下，顶部g -四重奏上腺嘌呤和胸腺嘧啶残基的相互作用以及底部g -四重奏下3端5个残基的G10中心点C18碱基对和一个折叠基序有助于结构稳定性。3-tail能够形成双分子预折叠结构，驱动kit*折叠成单个g -四重体。有趣的是，kit* g -四重体形成的动力学符合转录过程的时间尺度，并可能证明动力学和热力学因素的相互作用，以理解c-KIT原癌基因表达的调控。
In the promoter of c-KIT proto-oncogene, whose deregulation has been implicated in many cancers, three G-rich regions (kit1, kit* and kit2) are able to fold into G-quadruplexes. While kit1 and kit2 have been studied in depth, little information is available on kit* folding behavior despite its key role in regulation of c-KIT transcription. Notably, kit* contains consensus sites for SP1 and AP2 transcription factors. Herein, a set of complementary spectroscopic and biophysical methods reveals that kit*, d[GGCGAGGAGGGGCGTGGCCGGC], adopts a chair type antiparallel G-quadruplex with two G-quartets at physiological relevant concentrations of KCl. Heterogeneous ensemble of structures is observed in the presence of Na+ and NH4+ ions, which however stabilize pre-folded structure. In the presence of K+ ions stacking interactions of adenine and thymine residues on the top G-quartet contribute to structural stability together with a G10 center dot C18 base pair and a fold-back motif of the five residues at the 3-terminal under the bottom G-quartet. The 3-tail enables formation of a bimolecular pre-folded structure that drives folding of kit* into a single G-quadruplex. Intriguingly, kinetics of kit* G-quadruplex formation matches timescale of transcriptional processes and might demonstrate interplay of kinetic and thermodynamic factors for understanding regulation of c-KIT proto-oncogene expression.