Zheng Wen, Guo Jinjing, Ma Shuyan, Sun Rong, Song Yihua, Chen Yuanmeng, Mao Renfang, Fan Yihui
Department of Pathogenic Biology, School of Medicine, Nantong University, Nantong, China; Laboratory of Medical Science, School of Medicine, Nantong University, Nantong, China.
Laboratory of Medical Science, School of Medicine, Nantong University, Nantong, China.
J Biol Chem. 2024 Dec;300(12):107954. doi: 10.1016/j.jbc.2024.107954. Epub 2024 Nov 2.
3'UTRs are recognized for their role in regulating mRNA turnover while the turnover of a specific group of mRNAs mediated by coding sequences (CDSs) remains poorly understood. N4BP1 is a critical inflammatory regulator in vivo with a molecular mechanism that is not yet clearly defined. Our study reveals that N4BP1 efficiently degrades its mRNA targets via CDS rather than the 3'-UTR. This CDS-dependent mRNA turnover mechanism appears to be a general feature of N4BP1, as evidenced by testing multiple mRNA substrates, such as Fos-C, Fos-B, Jun-B, and C-X-C motif chemokine ligand 1. Detailed mapping of the motif identified a crucial 33-nt (289-322) sequence near the 5'-end of Fos-C-CDS, where the presence of polyC is necessary for N4BP1-mediated degradation. Functional studies involving domain deletion and point mutations showed that both the K homology and N4BP1, YacP-like nuclease domains are essential for N4BP1 to restrict mRNA substrates. The function of N4BP1 in mRNA turnover is not dependent on nonsense-mediated decay as it efficiently restricts mRNA substrates even in cells deficient in UPF1, UPF3A, and UPF3B. Additionally, the function of N4BP1 is not reliant on LUC7L3 despite its known association with this protein. Our findings suggest that N4BP1 acts as an endoribonuclease to degrade mRNA substrates primarily through CDSs containing a C-rich motif.
3'非翻译区（3'UTRs）因其在调节mRNA周转中的作用而被认可，而由编码序列（CDSs）介导的特定一组mRNA的周转仍知之甚少。N4BP1是体内一种关键的炎症调节因子，其分子机制尚未明确。我们的研究表明，N4BP1通过编码序列而非3'-非翻译区有效地降解其mRNA靶标。这种依赖于编码序列的mRNA周转机制似乎是N4BP1的一个普遍特征，通过测试多种mRNA底物，如Fos-C、Fos-B、Jun-B和C-X-C基序趋化因子配体1可以证明这一点。对该基序的详细定位确定了Fos-C编码序列5'-末端附近一个关键的33个核苷酸（289-322）序列，其中多聚C的存在是N4BP1介导降解所必需的。涉及结构域缺失和点突变的功能研究表明，K同源结构域和N4BP1、YacP样核酸酶结构域对于N4BP1限制mRNA底物都是必不可少的。N4BP1在mRNA周转中的功能不依赖于无义介导的衰变，因为即使在缺乏UPF1、UPF3A和UPF3B的细胞中，它也能有效地限制mRNA底物。此外，尽管已知N4BP1与LUC7L3有关联，但其功能并不依赖于LUC7L3。我们的研究结果表明，N4BP1作为一种核糖核酸内切酶，主要通过含有富含C基序的编码序列来降解mRNA底物。
