Guanine is indispensable for immunoglobulin switch region RNA-DNA hybrid formation.
Guanine is indispensable for immunoglobulin switch region RNA-DNA hybrid formation.
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DOI：
10.1093/jmicro/dfi058
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发表时间：
2005-08
期刊：
影响因子：
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通讯作者：
R. Mizuta;Midori Mizuta;D. Kitamura
中科院分区：
文献类型：
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作者：
R. Mizuta;Midori Mizuta;D. Kitamura
这表明，开关（S）区域RNA-DNA杂交体的形成和随后产生的高阶染色质结构，包括R环启动了免疫球蛋白基因的类别转换重组。这种重组的主要因素是S区衍生的非编码RNA。然而，这种富含鸟嘌呤（G-丰富）转录的生化特征知之甚少。本研究利用原子力显微镜（AFM）分析这种富含G的RNA的结构。将体外转录的S区RNA涂布在云母板上，风干并在空气中通过非接触式AFM观察。富含G的转录物倾向于在模板DNA上聚集并产生更高阶的RNA-DNA复合物。然而，转录本，纳入鸟嘌呤类似物作为鸟嘌呤的替代品既不聚集，也不产生高阶结构。在转录的RNA中掺入鸟嘌呤类似物部分地破坏与鸟嘌呤相关的氢键，例如沃森-克里克GC-碱基对和Hoogsteen键GG-碱基对。因此，S区RNA的聚集和高级RNA-DNA复合物的产生归因于鸟嘌呤的氢键。
It is suggested that the formation of the switch (S) region RNA-DNA hybrid and the subsequent generation of higher-order chromatin structures including R-loop initiate a class switch recombination of the immunoglobulin gene. The primary factor of this recombination is the S-region derived noncoding RNA. However, the biochemical character of this guanine-rich (G-rich) transcript is poorly understood. The present study was performed to analyze the structure of this G-rich RNA using atomic force microscope (AFM). The in vitro transcribed S-region RNA was spread on a mica plate, air-dried and observed by non-contact mode AFM in air. The G-rich transcripts tend to aggregate on the template DNA and to generate a higher-order RNA-DNA complex. However, the transcripts that incorporated guanine analogues as substitutes for guanine neither aggregated nor generated higher-order structures. Incorporation of guanine analogues in transcribed RNA partially disrupts hydrogen bonds related to guanine, such as Watson-Crick GC-base pair and Hoogsteen bond GG-base pair. Thus, aggregation of S-region RNA and generation of the higher-order RNA-DNA complex are attributed to hydrogen bonds of guanine.