State Key Laboratory for Protein and Plant Gene Research, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, Beijing, 100871, China.
Beijing Advanced Center of RNA Biology (BEACON), Peking University, Beijing, 100871, China.
Nat Commun. 2024 Mar 13;15(1):2261. doi: 10.1038/s41467-024-46499-y.
The occurrence of NAD as a non-canonical RNA cap has been demonstrated in diverse organisms. TIR domain-containing proteins present in all kingdoms of life act in defense responses and can have NADase activity that hydrolyzes NAD. Here, we show that TIR domain-containing proteins from several bacterial and one archaeal species can remove the NAM moiety from NAD-capped RNAs (NAD-RNAs). We demonstrate that the deNAMing activity of AbTir (from Acinetobacter baumannii) on NAD-RNA specifically produces a cyclic ADPR-RNA, which can be further decapped in vitro by known decapping enzymes. Heterologous expression of the wild-type but not a catalytic mutant AbTir in E. coli suppressed cell propagation and reduced the levels of NAD-RNAs from a subset of genes before cellular NAD levels are impacted. Collectively, the in vitro and in vivo analyses demonstrate that TIR domain-containing proteins can function as a deNAMing enzyme of NAD-RNAs, raising the possibility of TIR domain proteins acting in gene expression regulation.
NAD 作为一种非典型的 RNA 帽的存在已经在多种生物中得到证实。在所有生命领域中存在的 TIR 结构域蛋白在防御反应中起作用，并且可以具有水解 NAD 的 NADase 活性。在这里，我们表明，来自几种细菌和一种古细菌物种的 TIR 结构域蛋白可以从 NAD 帽 RNA（NAD-RNA）上去除 NAM 部分。我们证明，AbTir（来自鲍曼不动杆菌）对 NAD-RNA 的去 NAM 活性特异性地产生环状 ADPR-RNA，其可以在体外进一步被已知的去帽酶去帽。野生型但不是催化突变体 AbTir 在大肠杆菌中的异源表达抑制细胞增殖，并降低了细胞 NAD 水平受到影响之前一组基因的 NAD-RNA 水平。总之，体外和体内分析表明，TIR 结构域蛋白可以作为 NAD-RNA 的去 NAM 酶发挥作用，这增加了 TIR 结构域蛋白在基因表达调控中发挥作用的可能性。
