Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, 20133 Milano, Italy.
Mol Cell. 2012 Jan 13;45(1):99-110. doi: 10.1016/j.molcel.2011.12.019.
The chemical identity and integrity of the genome is challenged by the incorporation of ribonucleoside triphosphates (rNTPs) in place of deoxyribonucleoside triphosphates (dNTPs) during replication. Misincorporation is limited by the selectivity of DNA replicases. We show that accumulation of ribonucleoside monophosphates (rNMPs) in the genome causes replication stress and has toxic consequences, particularly in the absence of RNase H1 and RNase H2, which remove rNMPs. We demonstrate that postreplication repair (PRR) pathways-MMS2-dependent template switch and Pol ζ-dependent bypass-are crucial for tolerating the presence of rNMPs in the chromosomes; indeed, we show that Pol ζ efficiently replicates over 1-4 rNMPs. Moreover, cells lacking RNase H accumulate mono- and polyubiquitylated PCNA and have a constitutively activated PRR. Our findings describe a crucial function for RNase H1, RNase H2, template switch, and translesion DNA synthesis in overcoming rNTPs misincorporated during DNA replication, and may be relevant for the pathogenesis of Aicardi-Goutières syndrome.
在复制过程中，核糖核苷三磷酸（rNTP）取代脱氧核苷三磷酸（dNTP）掺入会对基因组的化学性质和完整性造成挑战。这种错误掺入受到 DNA 复制酶的选择性限制。我们发现，核糖核苷酸单磷酸（rNMP）在基因组中的积累会导致复制应激，并产生毒性后果，尤其是在缺乏 RNase H1 和 RNase H2 的情况下，因为它们可以去除 rNMP。我们证明，复制后修复（PRR）途径——MMS2 依赖性模板转换和 Pol ζ 依赖性绕过——对于耐受染色体中 rNMP 的存在至关重要；实际上，我们表明 Pol ζ 可以有效地复制超过 1-4 个 rNMP。此外，缺乏 RNase H 的细胞会积累单泛素化和多泛素化的 PCNA，并且 PRR 持续激活。我们的发现描述了 RNase H1、RNase H2、模板转换和跨损伤 DNA 合成在克服 DNA 复制过程中错误掺入的 rNTP 方面的关键功能，这可能与 Aicardi-Goutières 综合征的发病机制有关。
