Département de Biochimie et Médecine Moléculaire, Faculté de médecine, Université de Montréal, 2900 Édouard Montpetit, Montréal, QC, H3T 1J4, Canada.
BMC Mol Cell Biol. 2021 Mar 4;22(1):16. doi: 10.1186/s12860-021-00352-y.
Staufen2 (STAU2) is an RNA binding protein involved in the posttranscriptional regulation of gene expression. In neurons, STAU2 is required to maintain the balance between differentiation and proliferation of neural stem cells through asymmetric cell division. However, the importance of controlling STAU2 expression for cell cycle progression is not clear in non-neuronal dividing cells. We recently showed that STAU2 transcription is inhibited in response to DNA-damage due to E2F1 displacement from the STAU2 gene promoter. We now study the regulation of STAU2 steady-state levels in unstressed cells and its consequence for cell proliferation.
CRISPR/Cas9-mediated and RNAi-dependent STAU2 depletion in the non-transformed hTERT-RPE1 cells both facilitate cell proliferation suggesting that STAU2 expression influences pathway(s) linked to cell cycle controls. Such effects are not observed in the CRISPR STAU2-KO cancer HCT116 cells nor in the STAU2-RNAi-depleted HeLa cells. Interestingly, a physiological decrease in the steady-state level of STAU2 is controlled by caspases. This effect of peptidases is counterbalanced by the activity of the CHK1 pathway suggesting that STAU2 partial degradation/stabilization fines tune cell cycle progression in unstressed cells. A large-scale proteomic analysis using STAU2/biotinylase fusion protein identifies known STAU2 interactors involved in RNA translation, localization, splicing, or decay confirming the role of STAU2 in the posttranscriptional regulation of gene expression. In addition, several proteins found in the nucleolus, including proteins of the ribosome biogenesis pathway and of the DNA damage response, are found in close proximity to STAU2. Strikingly, many of these proteins are linked to the kinase CHK1 pathway, reinforcing the link between STAU2 functions and the CHK1 pathway. Indeed, inhibition of the CHK1 pathway for 4 h dissociates STAU2 from proteins involved in translation and RNA metabolism.
These results indicate that STAU2 is involved in pathway(s) that control(s) cell proliferation, likely via mechanisms of posttranscriptional regulation, ribonucleoprotein complex assembly, genome integrity and/or checkpoint controls. The mechanism by which STAU2 regulates cell growth likely involves caspases and the kinase CHK1 pathway.
Staufen2（STAU2）是一种参与基因表达转录后调控的 RNA 结合蛋白。在神经元中，STAU2 通过不对称细胞分裂来维持神经干细胞分化和增殖之间的平衡。然而，在非神经分裂细胞中，控制 STAU2 表达对细胞周期进程的重要性尚不清楚。我们最近表明，由于 E2F1 从 STAU2 基因启动子上的位移，STAU2 转录会在 DNA 损伤时受到抑制。我们现在研究未受应激的细胞中 STAU2 稳定水平的调节及其对细胞增殖的影响。
非转化 hTERT-RPE1 细胞中 CRISPR/Cas9 介导和 RNAi 依赖性 STAU2 耗竭均促进细胞增殖，表明 STAU2 表达影响与细胞周期控制相关的途径。在 CRISPR STAU2-KO 癌症 HCT116 细胞或 STAU2-RNAi 耗竭的 HeLa 细胞中观察不到这种效应。有趣的是，STAU2 的稳定水平的生理性降低受半胱天冬酶控制。蛋白酶的这种作用被 CHK1 途径的活性所抵消，表明 STAU2 的部分降解/稳定微调了未受应激细胞的细胞周期进程。使用 STAU2/生物素酶融合蛋白进行的大规模蛋白质组学分析鉴定了已知参与 RNA 翻译、定位、剪接或衰变的 STAU2 相互作用物，证实了 STAU2 在基因表达的转录后调控中的作用。此外，在核仁中发现的几种蛋白质，包括核糖体生物发生途径和 DNA 损伤反应的蛋白质，与 STAU2 接近。引人注目的是，这些蛋白质中有许多与激酶 CHK1 途径有关，这加强了 STAU2 功能与 CHK1 途径之间的联系。事实上，抑制 CHK1 途径 4 小时会使 STAU2 与参与翻译和 RNA 代谢的蛋白质分离。
这些结果表明，STAU2 参与了控制细胞增殖的途径，可能通过转录后调控、核糖核蛋白复合物组装、基因组完整性和/或检查点控制的机制。STAU2 调节细胞生长的机制可能涉及半胱天冬酶和激酶 CHK1 途径。
