Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba, 277-8562, Japan.
Nat Commun. 2019 Apr 29;10(1):1960. doi: 10.1038/s41467-019-09966-5.
Lin28-dependent oligo-uridylylation of precursor let-7 (pre-let-7) by terminal uridylyltransferase 4/7 (TUT4/7) represses let-7 expression by blocking Dicer processing, and regulates cell differentiation and proliferation. The interaction between the Lin28:pre-let-7 complex and the N-terminal Lin28-interacting module (LIM) of TUT4/7 is required for pre-let-7 oligo-uridylylation by the C-terminal catalytic module (CM) of TUT4/7. Here, we report crystallographic and biochemical analyses of the LIM of human TUT4. The LIM consists of the N-terminal Cys2His2-type zinc finger (ZF) and the non-catalytic nucleotidyltransferase domain (nc-NTD). The ZF of LIM adopts a distinct structural domain, and its structure is homologous to those of double-stranded RNA binding zinc fingers. The interaction between the ZF and pre-let-7 stabilizes the Lin28:pre-let-7:TUT4 ternary complex, and enhances the oligo-uridylylation reaction by the CM. Thus, the ZF in LIM and the zinc-knuckle in the CM, which interacts with the oligo-uridylylated tail, together facilitate Lin28-dependent pre-let-7 oligo-uridylylation.
Lin28 通过末端尿苷转移酶 4/7（TUT4/7）依赖的寡聚尿苷酸化作用抑制 pre-let-7 的表达，通过阻断 Dicer 加工来抑制 let-7 的表达，并调节细胞分化和增殖。Lin28:pre-let-7 复合物与 TUT4/7 的 N 端 Lin28 相互作用模块（LIM）之间的相互作用对于 TUT4/7 的 C 端催化模块（CM）对 pre-let-7 的寡聚尿苷酸化是必需的。在这里，我们报告了人 TUT4 的 LIM 的晶体学和生化分析。LIM 由 N 端 Cys2His2 型锌指（ZF）和非催化核苷酸转移酶结构域（nc-NTD）组成。LIM 的 ZF 采用独特的结构域，其结构与双链 RNA 结合锌指的结构同源。ZF 与 pre-let-7 的相互作用稳定了 Lin28:pre-let-7:TUT4 三元复合物，并增强了 CM 的寡聚尿苷酸化反应。因此，LIM 中的 ZF 和与寡聚尿苷酸化尾部相互作用的 CM 中的锌指共同促进 Lin28 依赖性 pre-let-7 寡聚尿苷酸化。
