A hybrid G-quadruplex structure formed between RNA and DNA explains the extraordinary stability of the mitochondrial R-loop

作者：Wanrooij Paulina H; Uhler Jay P; Shi Yonghong; Westerlund Fredrik; Falkenberg Maria; Gustafsson Claes M^*

来源：Nucleic Acids Research, 2012, 40(20): 10334-10344.

DOI：10.1093/nar/gks802

In human mitochondria the transcription machinery generates the RNA primers needed for initiation of DNA replication. A critical feature of the leading-strand origin of mitochondrial DNA replication is a CG-rich element denoted conserved sequence block II (CSB II). During transcription of CSB II, a G-quadruplex structure forms in the nascent RNA, which stimulates transcription termination and primer formation. Previous studies have shown that the newly synthesized primers form a stable and persistent RNA-DNA hybrid, a R-loop, near the leading-strand origin of DNA replication. We here demonstrate that the unusual behavior of the RNA primer is explained by the formation of a stable G-quadruplex structure, involving the CSB II region in both the nascent RNA and the non-template DNA strand. Based on our data, we suggest that G-quadruplex formation between nascent RNA and the non-template DNA strand may be a regulated event, which decides the fate of RNA primers and ultimately the rate of initiation of DNA synthesis in human mitochondria.

• 出版日期2012-11