Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (A*STAR), 61 Biopolis Drive, Proteos, Singapore, 138673, Republic of Singapore.
Department of Obstetrics and Gynecology, Guangdong Provincial Key Laboratory of Major Obstetric Diseases, Guangzhou, China.
Nat Commun. 2023 Oct 13;14(1):6464. doi: 10.1038/s41467-023-42078-9.
Regulation of global transcription output is important for normal development and disease, but little is known about the mechanisms involved. DNA topoisomerase I (TOP1) is an enzyme well-known for its role in relieving DNA supercoils for enabling transcription. Here, we report a non-enzymatic function of TOP1 that downregulates RNA synthesis. This function is dependent on specific DNA-interacting residues located on a conserved protein surface. A loss-of-function knock-in mutation on this surface, R548Q, is sufficient to cause hypertranscription and alter differentiation outcomes in mouse embryonic stem cells (mESCs). Hypertranscription in mESCs is accompanied by reduced TOP1 chromatin binding and change in genomic supercoiling. Notably, the mutation does not impact TOP1 enzymatic activity; rather, it diminishes TOP1-DNA binding and formation of compact protein-DNA structures. Thus, TOP1 exhibits opposing influences on transcription through distinct activities which are likely to be coordinated. This highlights TOP1 as a safeguard of appropriate total transcription levels in cells.
全球转录输出的调控对正常发育和疾病至关重要，但涉及的机制知之甚少。DNA 拓扑异构酶 I（TOP1）是一种众所周知的酶，其作用是缓解 DNA 超螺旋以促进转录。在这里，我们报告了 TOP1 的一种非酶功能，即下调 RNA 合成。该功能依赖于位于保守蛋白质表面上的特定 DNA 相互作用残基。该表面上的功能丧失性点突变 R548Q 足以导致小鼠胚胎干细胞（mESC）中超转录和分化结果的改变。mESC 中超转录伴随着 TOP1 染色质结合减少和基因组超螺旋变化。值得注意的是，该突变不影响 TOP1 的酶活性；相反，它降低了 TOP1-DNA 结合和紧凑的蛋白质-DNA 结构的形成。因此，TOP1 通过不同的活性对转录产生相反的影响，这些活性可能是协调的。这凸显了 TOP1 作为细胞中适当总转录水平的保障。
