Tan Tan, Chen Zhe, Lei Yan, Zhu Yan, Liang Qianjin
Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing, China.
Beijing Key Laboratory of Gene Resource and Molecular Development / Beijing Key Laboratory of Gene Engineering Drugs & Biological Technology, Beijing Normal University, Beijing, China.
PLoS One. 2014 Mar 14;9(3):e91937. doi: 10.1371/journal.pone.0091937. eCollection 2014.
CENP-B is a highly conserved protein that facilitates the assembly of specific centromere structures both in interphase nuclei and on mitotic chromosomes. INMAP is a conserved protein that localizes at nucleus in interphase cells and at mitotic apparatus in mitotic cells. Our previous results showed that INMAP over-expression leads to spindle defects, mitotic arrest and formation of polycentrosomal and multinuclear cells, indicating that INMAP may modulate the function of (a) key protein(s) in mitotic apparatus. In this study, we demonstrate that INMAP interacts with CENP-B and promotes cleavage of the N-terminal DNA binding domain from CENP-B. The cleaved CENP-B cannot associate with centromeres and thus lose its centromere-related functions. Consistent with these results, CENP-B in INMAP knockdown cells becomes more diffused around kinetochores. Although INMAP knockdown cells do not exhibit gross defects in mitotic spindle formation, these cells go through mitosis, especially prophase and metaphase, with different relative timing, indicating subtle abnormality. These results identify INMAP as a model regulator of CENP-B and support the notion that INMAP regulates mitosis through modulating CENP-B-mediated centromere organization.
着丝粒蛋白B（CENP - B）是一种高度保守的蛋白质，它在间期细胞核和有丝分裂染色体上都有助于特定着丝粒结构的组装。INMAP是一种保守蛋白，在间期细胞中定位于细胞核，在有丝分裂细胞中定位于有丝分裂装置。我们之前的结果表明，INMAP过表达会导致纺锤体缺陷、有丝分裂停滞以及多中心体和多核细胞的形成，这表明INMAP可能调节有丝分裂装置中关键蛋白的功能。在本研究中，我们证明INMAP与CENP - B相互作用，并促进CENP - B的N端DNA结合结构域的切割。切割后的CENP - B不能与着丝粒结合，从而失去其与着丝粒相关的功能。与这些结果一致，在INMAP敲低细胞中的CENP - B在动粒周围变得更加分散。虽然INMAP敲低细胞在有丝分裂纺锤体形成中没有表现出明显缺陷，但这些细胞经历有丝分裂，特别是前期和中期，其相对时间不同，表明存在细微异常。这些结果确定INMAP是CENP - B的一种调节模型，并支持INMAP通过调节CENP - B介导的着丝粒组织来调节有丝分裂的观点。
