Institute of Bioinformatics and Biosignal Transduction, College of Bioscience and Biotechnology, National Cheng-Kung University, Tainan 701, Taiwan.
Institute of Bioinformatics and Biosignal Transduction, College of Bioscience and Biotechnology, National Cheng-Kung University, Tainan 701, Taiwan; Institute of Basic Medical Sciences, National Cheng-Kung University, Tainan 701, Taiwan.
J Biol Chem. 2011 Dec 23;286(51):43816-43829. doi: 10.1074/jbc.M111.310979. Epub 2011 Oct 13.
Most studies on heat shock protein 90 (Hsp90) have focused on the involvement of Hsp90 in the interphase, whereas the role of this protein in the nucleus during mitosis remains largely unclear. In this study, we found that the level of the acetylated form of Hsp90 decreased dramatically during mitosis, which indicates more chaperone activity during mitosis. We thus probed proteins that interacted with Hsp90 by liquid chromatography/mass spectrometry (LC/MS) and found that nucleolin was one of those interacting proteins during mitosis. The nucleolin level decreased upon geldanamycin treatment, and Hsp90 maintained the cyclin-dependent kinase 1 (CDK1) activity to phosphorylate nucleolin at Thr-641/707. Mutation of Thr-641/707 resulted in the destabilization of nucleolin in mitosis. We globally screened the level of mitotic mRNAs and found that 229 mRNAs decreased during mitosis in the presence of geldanamycin. Furthermore, a bioinformatics tool and an RNA immunoprecipitation assay found that 16 mRNAs, including cadherin and Bcl-xl, were stabilized through the recruitment of nucleolin to the 3'-untranslated regions (3'-UTRs) of those genes. Overall, strong correlations exist between the up-regulation of Hsp90, nucleolin, and the mRNAs related to tumorigenesis of the lung. Our findings thus indicate that nucleolin stabilized by Hsp90 contributes to the lung tumorigenesis by increasing the level of many tumor-related mRNAs during mitosis.
大多数关于热休克蛋白 90（Hsp90）的研究都集中在 Hsp90 参与间期的作用上，而其在有丝分裂过程中在核内的作用在很大程度上仍不清楚。在这项研究中，我们发现 Hsp90 的乙酰化形式在有丝分裂过程中急剧下降，这表明有丝分裂过程中有更多的伴侣活性。因此，我们通过液相色谱/质谱（LC/MS）探测与 Hsp90 相互作用的蛋白质，发现核仁蛋白是有丝分裂过程中与 Hsp90 相互作用的蛋白质之一。在用格尔德霉素处理后，核仁蛋白的水平下降，Hsp90 维持细胞周期蛋白依赖性激酶 1（CDK1）的活性，使核仁蛋白在 Thr-641/707 处磷酸化。Thr-641/707 的突变导致核仁蛋白在有丝分裂中不稳定。我们对有丝分裂 mRNA 的水平进行了全局筛选，发现有丝分裂过程中在存在格尔德霉素的情况下有 229 个 mRNA 减少。此外，生物信息学工具和 RNA 免疫沉淀试验发现，包括钙粘蛋白和 Bcl-xl 在内的 16 个 mRNA 通过核仁蛋白募集到这些基因的 3'非翻译区（3'-UTRs）而稳定。总体而言，Hsp90、核仁蛋白和与肺癌发生相关的 mRNA 的上调之间存在很强的相关性。我们的研究结果表明，Hsp90 稳定的核仁蛋白通过在有丝分裂过程中增加许多与肿瘤相关的 mRNA 的水平，促进肺癌的发生。
