SFR, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
SFR, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
DNA Repair (Amst). 2019 Dec;84:102736. doi: 10.1016/j.dnarep.2019.102736. Epub 2019 Oct 23.
Eukaryotic RNases H2 have dual functions in initiating the removal of ribonucleoside monophosphates (rNMPs) incorporated by DNA polymerases during DNA synthesis and in cleaving the RNA moiety of RNA/DNA hybrids formed during transcription and retrotransposition. The other major cellular RNase H, RNase H1, shares the hybrid processing activity, but not all substrates. After RNase H2 incision at the rNMPs in DNA the Ribonucleotide Excision Repair (RER) pathway completes the removal, restoring dsDNA. The development of the RNase H2-RED (Ribonucleotide Excision Defective) mutant enzyme, which can process RNA/DNA hybrids but is unable to cleave rNMPs embedded in DNA has unlinked the two activities and illuminated the roles of RNase H2 in cellular metabolism. Studies mostly in Saccharomyces cerevisiae, have shown both activities of RNase H2 are necessary to maintain genome integrity and that RNase H1 and H2 have overlapping as well as distinct RNA/DNA hybrid substrates. In mouse RNase H2-RED confirmed that rNMPs in DNA during embryogenesis induce lethality in a p53-dependent DNA damage response. In mammalian cell cultures, RNase H2-RED helped identifying DNA lesions produced by Top1 cleavage at rNMPs and led to determine that RNase H2 participates in the retrotransposition of LINE-1 elements. In this review, we summarize the studies and conclusions reached by utilization of RNase H2-RED enzyme in different model systems.
真核生物 RNase H2 具有双重功能，既能在 DNA 合成过程中启动 DNA 聚合酶掺入的核糖核苷酸单磷酸 (rNMP) 的去除，又能切割转录和逆转录过程中形成的 RNA/DNA 杂交体的 RNA 部分。另一种主要的细胞 RNase H1 具有杂交体加工活性，但不是所有的底物。在 RNase H2 在 DNA 中的 rNMP 处切割后，核苷酸切除修复 (RER) 途径完成去除，恢复双链 DNA。开发出的 RNase H2-RED（核苷酸切除缺陷）突变酶能够处理 RNA/DNA 杂交体，但不能切割嵌入 DNA 中的 rNMP，这种酶将两种活性分离，并阐明了 RNase H2 在细胞代谢中的作用。在酿酒酵母中的研究表明，RNase H2 的两种活性都需要维持基因组的完整性，并且 RNase H1 和 H2 具有重叠的以及不同的 RNA/DNA 杂交体底物。在小鼠 RNase H2-RED 中证实，胚胎发生过程中 DNA 中的 rNMP 会在 p53 依赖的 DNA 损伤反应中诱导致死。在哺乳动物细胞培养物中，RNase H2-RED 有助于鉴定在 rNMP 处由 Top1 切割产生的 DNA 损伤，并确定 RNase H2 参与 LINE-1 元件的逆转录转位。在这篇综述中，我们总结了利用不同模型系统中的 RNase H2-RED 酶进行的研究和得出的结论。
