小柯机器人

英国牛津大学Ivan Ahel、萨里大学Graham R. Stewart等研究人员合作揭示DarT对DNA碱基进行ADP-核苷酸化的分子基础。相关论文于2021年8月18日在线发表在《自然》杂志上。

研究人员表明，胸苷碱基上DNA的特异性、可逆性ADP-核糖基化是通过DarT-DarG毒素-抗毒素系统在细胞内发生的，该系统在各种细菌（包括全球的病原体，如结核分枝杆菌、肠致病性大肠杆菌和铜绿假单胞菌）中发现。研究人员报告了DarT的结构，这表明该蛋白是PARP家族的一个分支成员。研究人员提供了该酶在无配体和反应前后状态下的一组高分辨率结构，揭示了一种专门的催化机制，包括一个关键的活性位点精氨酸，扩展了典型ADP-核糖基转移酶的类型。与PARP-HPF1（一种成熟的DNA修复蛋白ADP-核糖基化复合物）进行比较，可以深入了解DarT类ADP-核糖基转移酶如何演变为特定的DNA修饰酶。这些结构和机制数据共同提供了这个PARP家族成员的细节，并有助于对核酸的ADP-核糖基化的基本理解。

研究人员还表明，由DarG抗毒素（作为非经典DNA修复因子运作）逆转的胸腺素连接的ADP-核糖DNA加合物不仅用于有针对性的DNA损伤以诱发毒性，而且还作为细胞进程的信号策略。以结核杆菌为例，研究人员表明DarT-DarG通过染色体复制起源处DNA的ADP-核糖基化来调节生长。

据介绍，ADP-核糖基转移酶利用NAD⁺催化底物ADP-核糖基化，从而调节细胞途径或对细菌的毒素介导的致病性作出贡献。可逆的ADP-核糖基化传统上被认为是一种蛋白质特异性修饰，但最近的体外研究表明核酸是靶标。

附：英文原文

Title: Molecular basis for DarT ADP-ribosylation of a DNA base

Author: Schuller, Marion, Butler, Rachel E., Ariza, Antonio, Tromans-Coia, Callum, Jankevicius, Gytis, Claridge, Tim D. W., Kendall, Sharon L., Goh, Shan, Stewart, Graham R., Ahel, Ivan

Issue&Volume: 2021-08-18

Abstract: ADP-ribosyltransferases use NAD+ to catalyse substrate ADP-ribosylation1, and thereby regulate cellular pathways or contribute to toxin-mediated pathogenicity of bacteria2,3,4. Reversible ADP-ribosylation has traditionally been considered a protein-specific modification5, but recent in vitro studies have suggested nucleic acids as targets6,7,8,9. Here we present evidence that specific, reversible ADP-ribosylation of DNA on thymidine bases occurs in cellulo through the DarT–DarG toxin–antitoxin system, which is found in a variety of bacteria (including global pathogens such as Mycobacterium tuberculosis, enteropathogenic Escherichia coli and Pseudomonas aeruginosa)10. We report the structure of DarT, which identifies this protein as a diverged member of the PARP family. We provide a set of high-resolution structures of this enzyme in ligand-free and pre- and post-reaction states, which reveals a specialized mechanism of catalysis that includes a key active-site arginine that extends the canonical ADP-ribosyltransferase toolkit. Comparison with PARP–HPF1, a well-established DNA repair protein ADP-ribosylation complex, offers insights into how the DarT class of ADP-ribosyltransferases evolved into specific DNA-modifying enzymes. Together, our structural and mechanistic data provide details of this PARP family member and contribute to a fundamental understanding of the ADP-ribosylation of nucleic acids. We also show that thymine-linked ADP-ribose DNA adducts reversed by DarG antitoxin (functioning as a noncanonical DNA repair factor) are used not only for targeted DNA damage to induce toxicity, but also as a signalling strategy for cellular processes. Using M. tuberculosis as an exemplar, we show that DarT–DarG regulates growth by ADP-ribosylation of DNA at the origin of chromosome replication.

DOI: 10.1038/s41586-021-03825-4

Source: https://www.nature.com/articles/s41586-021-03825-4

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
官方网址：http://www.nature.com/
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