Department of Biotechnology, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan.
J Cell Sci. 2011 Feb 1;124(Pt 3):394-404. doi: 10.1242/jcs.063347.
Segregation of chromosomes during cell division requires correct formation of mitotic spindles. Here, we show that a scaffold attachment factor A (SAF-A), also known as heterogeneous nuclear ribonucleoprotein-U, contributes to the attachment of spindle microtubules (MTs) to kinetochores and spindle organization. During mitosis, SAF-A was localized at the spindles, spindle midzone and cytoplasmic bridge. Depletion of SAF-A by RNA interference induced mitotic delay and defects in chromosome alignment and spindle assembly. We found that SAF-A specifically co-immunoprecipitated with the chromosome peripheral protein nucleolin and the spindle regulators Aurora-A and TPX2, indicating that SAF-A is associated with nucleolin and the Aurora-A-TPX2 complex. SAF-A was colocalized with TPX2 and Aurora-A in spindle poles and MTs. Elimination of TPX2 or Aurora-A from cells abolished the association of SAF-A with the mitotic spindle. Interestingly, SAF-A can bind to MTs and contributes to the targeting of Aurora-A to mitotic spindle MTs. Our finding indicates that SAF-A is a novel spindle regulator that plays an essential role in kinetochore-MT attachment and mitotic spindle organization.
有丝分裂过程中染色体的分离需要有丝分裂纺锤体的正确形成。在这里，我们发现支架附着因子 A（SAF-A），也称为异质性核核糖核蛋白-U，有助于纺锤体微管（MT）与动粒的附着和纺锤体的组织。在有丝分裂过程中，SAF-A 定位于纺锤体、纺锤体中间区和细胞质桥。通过 RNA 干扰耗尽 SAF-A 会导致有丝分裂延迟以及染色体排列和纺锤体组装的缺陷。我们发现 SAF-A 特异性地与染色体外周蛋白核仁蛋白以及纺锤体调节因子 Aurora-A 和 TPX2 共免疫沉淀，表明 SAF-A 与核仁蛋白和 Aurora-A-TPX2 复合物相关。SAF-A 与 TPX2 和 Aurora-A 在纺锤体极和 MT 中共定位。从细胞中消除 TPX2 或 Aurora-A 会消除 SAF-A 与有丝分裂纺锤体的关联。有趣的是，SAF-A 可以结合到 MT 上，并有助于将 Aurora-A 靶向有丝分裂纺锤体 MT。我们的发现表明，SAF-A 是一种新型的纺锤体调节因子，在动粒-MT 附着和有丝分裂纺锤体组织中发挥着重要作用。
