复制蛋白A作为R环传感器和核糖核酸酶H1调节剂的功能。
Functions of Replication Protein A as a Sensor of R Loops and a Regulator of RNaseH1.
作者信息
Nguyen Hai Dang, Yadav Tribhuwan, Giri Sumanprava, Saez Borja, Graubert Timothy A, Zou Lee
机构信息
Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA.
Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA; Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
出版信息
Mol Cell. 2017 Mar 2;65(5):832-847.e4. doi: 10.1016/j.molcel.2017.01.029.
R loop, a transcription intermediate containing RNA:DNA hybrids and displaced single-stranded DNA (ssDNA), has emerged as a major source of genomic instability. RNaseH1, which cleaves the RNA in RNA:DNA hybrids, plays an important role in R loop suppression. Here we show that replication protein A (RPA), an ssDNA-binding protein, interacts with RNaseH1 and colocalizes with both RNaseH1 and R loops in cells. In vitro, purified RPA directly enhances the association of RNaseH1 with RNA:DNA hybrids and stimulates the activity of RNaseH1 on R loops. An RPA binding-defective RNaseH1 mutant is not efficiently stimulated by RPA in vitro, fails to accumulate at R loops in cells, and loses the ability to suppress R loops and associated genomic instability. Thus, in addition to sensing DNA damage and replication stress, RPA is a sensor of R loops and a regulator of RNaseH1, extending the versatile role of RPA in suppression of genomic instability.
R环是一种包含RNA:DNA杂交体和置换单链DNA（ssDNA）的转录中间体，已成为基因组不稳定的主要来源。核糖核酸酶H1（RNaseH1）可切割RNA:DNA杂交体中的RNA，在抑制R环方面发挥重要作用。在这里，我们表明，单链DNA结合蛋白复制蛋白A（RPA）与RNaseH1相互作用，并在细胞中与RNaseH1和R环共定位。在体外，纯化的RPA直接增强RNaseH1与RNA:DNA杂交体的结合，并刺激RNaseH1对R环的活性。RPA结合缺陷的RNaseH1突变体在体外不能被RPA有效刺激，无法在细胞中的R环处积累，并且失去了抑制R环和相关基因组不稳定的能力。因此，除了感知DNA损伤和复制应激外，RPA还是R环的传感器和RNaseH1的调节剂，扩展了RPA在抑制基因组不稳定方面的多种作用。
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