Liu R-M, Tian X-Y, Huang X-T, Zhou H
College of Life Sciences, Nankai University, Tianjin, P. R. China.
Folia Biol (Praha). 2013;59(3):105-9.
Serine 7 of centromere protein A (CENP-A) is a very important mitosis-specific phosphorylation site. In this study, we demonstrate the subcellular distribution of Ser7 phosphorylated CENP-A during mitosis in MCF-7 cells. The Ser7 phosphorylation of CENP-A was observed beginning at prophase at centromeres. Upon progression of mitosis, the fluorescence signals emerged in the central region of the metaphase plate and were maintained until anaphase at centromeres. At late anaphase, the fluorescence signals moved to the midzone gradually and transferred from the centromere to the midbody completely at telophase. They were compacted into the centre of the midbody in a thin cylinder consisting of a sandglass-like "mitotic machine" with microtubules and condensed chromosome. We also found that Ser10 phosphorylated H3 and Thr11 phosphorylated H3 were co-localized at the midbody in two bell-like symmetrical bodies with Ser7 phosphorylated CENP-A during the terminal stage of cytokinesis. Midbody isolation and immunoblotting experiments also indicated that Ser7 phosphorylated CENP-A are components of the midbody. These findings suggest that Ser7 phosphorylated CENP-A acts as a chromosomal passenger protein and may play an important role in cytokinesis.
着丝粒蛋白A（CENP-A）的丝氨酸7是一个非常重要的有丝分裂特异性磷酸化位点。在本研究中，我们展示了丝氨酸7磷酸化的CENP-A在MCF-7细胞有丝分裂过程中的亚细胞分布。在有丝分裂前期，在着丝粒处观察到CENP-A的丝氨酸7磷酸化。随着有丝分裂的进行，荧光信号出现在中期板的中央区域，并一直维持到后期的着丝粒处。在后期末期，荧光信号逐渐移向中间区，并在末期从着丝粒完全转移到中间体。它们在由微管和浓缩染色体组成的沙漏状“有丝分裂机器”的细圆柱体中被压实到中间体的中心。我们还发现，在胞质分裂末期，丝氨酸10磷酸化的H3和苏氨酸11磷酸化的H3与丝氨酸7磷酸化的CENP-A共定位于中间体的两个钟形对称体中。中间体分离和免疫印迹实验也表明，丝氨酸7磷酸化的CENP-A是中间体的组成成分。这些发现表明，丝氨酸7磷酸化的CENP-A作为一种染色体乘客蛋白，可能在胞质分裂中发挥重要作用。
