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8-Oxo-7,8-dihydroguanine in the Context of a Gene Promoter G-Quadruplex Is an On–Off Switch for Transcription
ACS Chemical Biology ( IF 3.5 ) Pub Date : 2017-08-28 00:00:00 , DOI: 10.1021/acschembio.7b00636
Aaron M. Fleming 1 , Judy Zhu 1 , Yun Ding 1 , Cynthia J. Burrows 1
Affiliation  

Interplay between DNA repair of the oxidatively modified base 8-oxo-7,8-dihydroguanine (OG) and transcriptional activation has been documented in mammalian genes. Previously, we synthesized OG into the VEGF potential G-quadruplex sequence (PQS) in the coding strand of a luciferase promoter to identify that base excision repair (BER) unmasked the G-quadruplex (G4) fold for gene activation. In the present work, OG was site-specifically synthesized into a luciferase reporter plasmid to follow the time-dependent expression in mammalian cells when OG in the VEGF PQS context was located in the coding vs template strands of the luciferase promoter. Removal of OG from the coding strand by OG glycosylase-1 (OGG1)-mediated BER upregulated transcription. When OG was in the template strand in the VEGF PQS context, transcription was downregulated by a BER-independent process. The time course changes in transcription show that repair in the template strand was more efficient than repair in the coding strand. Promoters were synthesized with an OG:A base pair that requires repair on both strands to yield a canonical G:C base pair. By monitoring the up/down luciferase expression, we followed the timing of repair of an OG:A base pair occurring on both strands in mammalian cells in which one lesion resides in a G-quadruplex loop and one in a potential i-motif. Depending on the strand in which OG resides, coding vs template, this modification is an up/downregulator of transcription that couples DNA repair with transcriptional regulation.

中文翻译:

在基因启动子G四联体的背景下8-氧7,8-二氢鸟嘌呤是转录的通断开关。

氧化修饰的碱基8-oxo-7,8-dihydroguanine(OG)的DNA修复与转录激活之间的相互作用已在哺乳动物基因中得到了证明。以前,我们在萤光素酶启动子的编码链中将OG合成到VEGF潜在的G-四链体序列(PQS)中,以鉴定碱基切除修复(BER)掩盖了G-四链体(G4)折叠的基因激活作用。在目前的工作中,OG被定点合成到荧光素酶报道质粒中,以追踪VEGF中OG在哺乳动物细胞中的时间依赖性表达。PQS上下文位于荧光素酶启动子的编码对模板链中。OG糖基化酶1(OGG1)介导的BER从编码链中去除OG上调了转录。当OG位于VEGF的模板链中时在PQS上下文中,转录被BER独立过程下调。转录的时程变化表明,模板链的修复比编码链的修复更有效。启动子与OG:A碱基对合成,该碱基对需要在两条链上进行修复才能产生规范的G:C碱基对。通过监测上/下荧光素酶的表达,我们跟踪了修复OG的时机:在哺乳动物细胞的两条链上都发生了一个碱基对,其中一个病变位于一个G-四链环中,一个位于一个潜在的i-基序中。根据OG所在的链,编码与模板的不同,这种修饰是转录的上调/下调,将DNA修复与转录调控结合在一起。
更新日期:2017-08-29
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