State Key Laboratory of Bioorganic and Natural Products Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, 200032, China.
Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, 201210, China.
Nat Commun. 2019 Oct 11;10(1):4664. doi: 10.1038/s41467-019-12710-8.
Signal transduction systems enable organisms to monitor their external environments and accordingly adjust the cellular processes. In mast cells, the second messenger ApA binds to the histidine triad nucleotide-binding protein 1 (HINT1), disrupts its interaction with the microphthalmia-associated transcription factor (MITF), and eventually activates the transcription of genes downstream of MITF in response to immunostimulation. How the HINT1 protein recognizes and is regulated by ApA remain unclear. Here, using eight crystal structures, biochemical experiments, negative stain electron microscopy, and cellular experiments, we report that ApA specifically polymerizes HINT1 in solution and in activated rat basophilic leukemia cells. The polymerization interface overlaps with the area on HINT1 for MITF interaction, suggesting a possible competitive mechanism to release MITF for transcriptional activation. The mechanism depends precisely on the length of the phosphodiester linkage of ApA. These results highlight a direct polymerization signaling mechanism by the second messenger.
信号转导系统使生物体能够监测其外部环境，并相应地调整细胞过程。在肥大细胞中，第二信使 ApA 与组氨酸三聚体核苷酸结合蛋白 1（HINT1）结合，破坏其与小眼畸形相关转录因子（MITF）的相互作用，并最终在免疫刺激下激活 MITF 下游基因的转录。HINT1 蛋白如何识别和被 ApA 调节仍不清楚。在这里，我们使用八个晶体结构、生化实验、负染电子显微镜和细胞实验，报告 ApA 特异性地在溶液中和激活的大鼠嗜碱性白血病细胞中聚合 HINT1。聚合界面与 HINT1 与 MITF 相互作用的区域重叠，表明可能存在一种竞争性机制来释放 MITF 以进行转录激活。该机制精确地依赖于 ApA 的磷酸二酯键的长度。这些结果突出了第二信使的直接聚合信号机制。
