Yang Jun, Adamian Michael, Li Tiansen
The Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA.
Mol Biol Cell. 2006 Feb;17(2):1033-40. doi: 10.1091/mbc.e05-10-0943. Epub 2005 Dec 7.
Rootletin, a major structural component of the ciliary rootlet, is located at the basal bodies and centrosomes in ciliated and nonciliated cells, respectively. Here we investigated its potential role in the linkage of basal bodies/centrioles and the mechanism involved in such linkages. We show that rootletin interacts with C-Nap1, a protein restricted at the ends of centrioles and functioning in centrosome cohesion in interphase cells. Their interaction in vivo is supported by their colocalization at the basal bodies/centrioles and coordinated association with the centrioles during the cell cycle. Ultrastructural examinations demonstrate that rootletin fibers connect the basal bodies in ciliated cells and are present both at the ends of and in between the pair of centrioles in nonciliated cells. The latter finding stands in contrast with C-Nap1, which is present only at the ends of the centrioles. Transient expression of C-Nap1 fragments dissociated rootletin fibers from the centrioles, resulting in centrosome separation in interphase. Overexpression of rootletin in cells caused multinucleation, micronucleation, and irregularity of nuclear shape and size, indicative of defects in chromosome separation. These data suggest that rootletin may function as a physical linker between the pair of basal bodies/centrioles by binding to C-Nap1.
根蛋白是纤毛小根的主要结构成分，分别位于纤毛细胞和非纤毛细胞的基体和中心体中。在这里，我们研究了它在基体/中心粒连接中的潜在作用以及这种连接所涉及的机制。我们发现根蛋白与C-Nap1相互作用，C-Nap1是一种局限于中心粒末端的蛋白质，在间期细胞的中心体黏附中发挥作用。它们在体内的相互作用得到了它们在基体/中心粒处共定位以及在细胞周期中与中心粒协调结合的支持。超微结构检查表明，根蛋白纤维连接纤毛细胞中的基体，并且存在于非纤毛细胞中一对中心粒的末端以及它们之间。后一发现与仅存在于中心粒末端的C-Nap1形成对比。C-Nap1片段的瞬时表达使根蛋白纤维与中心粒分离，导致间期中心体分离。在细胞中过表达根蛋白会导致多核化、微核化以及核形状和大小的不规则，这表明染色体分离存在缺陷。这些数据表明，根蛋白可能通过与C-Nap1结合而作为一对基体/中心粒之间的物理连接物发挥作用。
