Tob2, an anti-proliferative protein, promotes deadenylation through recruiting Caf1 deadenylase to the mRNA poly(A) tail by simultaneously interacting with both Caf1 and poly(A)-binding protein (PABP). Previously, we found that changes in Tob2 phosphorylation can alter its PABP-binding ability and deadenylation-promoting function. However, it remained unknown regarding the relevant kinase(s). Moreover, it was unclear whether Tob2 phosphorylation modulates the transcriptome and whether the phosphorylation is linked to Tob2's anti-proliferative function. In this study, we found that c-Jun N-terminal kinase (JNK) increases phosphorylation of Tob2 at many Ser/Thr sites in the intrinsically disordered region (IDR) that contains two separate PABP-interacting PAM2 motifs. JNK-induced phosphorylation or phosphomimetic mutations at these sites weaken the Tob2-PABP interaction. In contrast, JNK-independent phosphorylation of Tob2 at serine 254 (S254) greatly enhances Tob2 interaction with PABP and its ability to promote deadenylation. We discovered that both PAM2 motifs are required for Tob2 to display these features. Combining mass spectrometry analysis, poly(A) size-distribution profiling, transcriptome-wide mRNA turnover analyses, and cell proliferation assays, we found that the phosphomimetic mutation at S254 (S254D) enhances Tob2's association with PABP, leading to accelerated deadenylation and decay of mRNAs globally. Moreover, the Tob2-S254D mutant accelerates the decay of many transcripts coding for cell-cycle related proteins and enhances anti-proliferation function. Our findings reveal a novel mechanism by which Ccr4-Not complex is recruited by Tob2 to the mRNA 3' poly(A)-PABP complex in a phosphorylation dependent manner to promote rapid deadenylation and decay across the transcriptome, eliciting transcriptome reprogramming and suppressed cell proliferation.

中文翻译：

---

Tob2 磷酸化调节全球 mRNA 转换以重塑转录组并影响细胞增殖

Tob2 是一种抗增殖蛋白，通过同时与 Caf1 和聚 (A) 结合蛋白 (PABP) 相互作用，通过将 Caf1 脱腺苷酸酶募集到 mRNA 聚 (A) 尾部来促进脱腺苷酸化。以前，我们发现 Tob2 磷酸化的变化可以改变其 PABP 结合能力和去腺苷酸化促进功能。然而，关于相关激酶仍然未知。此外，尚不清楚 Tob2 磷酸化是否调节转录组以及磷酸化是否与 Tob2 的抗增殖功能有关。在这项研究中，我们发现 c-Jun N 末端激酶 (JNK) 增加了本质无序区域 (IDR) 中许多 Ser/Thr 位点的 Tob2 磷酸化，该区域包含两个独立的 PABP 相互作用 PAM2 基序。JNK 在这些位点诱导的磷酸化或拟磷酸化突变削弱了 Tob2-PABP 的相互作用。相比之下，Tob2 在丝氨酸 254 (S254) 的 JNK 独立磷酸化大大增强了 Tob2 与 PABP 的相互作用及其促进去腺苷酸化的能力。我们发现 Tob2 需要两个 PAM2 主题才能显示这些特征。结合质谱分析、poly(A) 大小分布分析、转录组范围的 mRNA 转换分析和细胞增殖分析，我们发现 S254 (S254D) 处的磷酸化突变增强了 Tob2 与 PABP 的关联，导致加速去腺苷酸化和衰变全球范围内的 mRNA。此外，Tob2-S254D 突变体加速了许多编码细胞周期相关蛋白的转录本的衰变，并增强了抗增殖功能。