Max Planck Institute for Developmental Biology, D-72076 Tübingen, Germany.
J Cell Biol. 2010 Apr 19;189(2):289-302. doi: 10.1083/jcb.200910141.
Decapping of eukaryotic messenger RNAs (mRNAs) occurs after they have undergone deadenylation, but how these processes are coordinated is poorly understood. In this study, we report that Drosophila melanogaster HPat (homologue of Pat1), a conserved decapping activator, interacts with additional decapping factors (e.g., Me31B, the LSm1-7 complex, and the decapping enzyme DCP2) and with components of the CCR4-NOT deadenylase complex. Accordingly, HPat triggers deadenylation and decapping when artificially tethered to an mRNA reporter. These activities reside, unexpectedly, in a proline-rich region. However, this region alone cannot restore decapping in cells depleted of endogenous HPat but also requires the middle (Mid) and the very C-terminal domains of HPat. We further show that the Mid and C-terminal domains mediate HPat recruitment to target mRNAs. Our results reveal an unprecedented role for the proline-rich region and the C-terminal domain of metazoan HPat in mRNA decapping and suggest that HPat is a component of the cellular mechanism that couples decapping to deadenylation in vivo.
真核信使 RNA（mRNA）的脱帽发生在它们经历去腺苷酸化之后，但这些过程是如何协调的还知之甚少。在这项研究中，我们报告说果蝇 HPat（Pat1 的同源物），一种保守的脱帽激活因子，与其他脱帽因子（例如 Me31B、LSm1-7 复合物和脱帽酶 DCP2）以及 CCR4-NOT 去腺苷酸酶复合物的成分相互作用。因此，HPat 当被人为地连接到 mRNA 报告子时，会引发去腺苷酸化和脱帽。这些活性出乎意料地存在于富含脯氨酸的区域中。然而，仅这一区域本身不能在耗尽内源性 HPat 的细胞中恢复脱帽，还需要 HPat 的中间（Mid）和非常 C 末端结构域。我们进一步表明，Mid 和 C 末端结构域介导 HPat 被募集到靶 mRNA。我们的结果揭示了后生动物 HPat 的富含脯氨酸区域和 C 末端结构域在 mRNA 脱帽中的前所未有的作用，并表明 HPat 是体内将脱帽与去腺苷酸化偶联的细胞机制的一个组成部分。
