Nakayama Yuji, Yamaguchi Naoto
Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba 260-8675, Japan.
Exp Cell Res. 2005 Apr 1;304(2):570-81. doi: 10.1016/j.yexcr.2004.11.027. Epub 2005 Jan 11.
Chk tyrosine kinase phosphorylates Src-family tyrosine kinases and suppresses their kinase activity. We recently showed that Chk localizes to the nucleus as well as the cytoplasm and inhibits cell proliferation. To investigate the role of nuclear Chk in proliferation, various Chk mutants were constructed and expressed. Nuclear localization of Chk-induced dynamic multi-lobulation of the nucleus and prolonged S phase of the cell cycle. The N-terminal domain of Chk and a portion of its kinase domain but not the kinase activity were responsible for induction of the multi-lobulation. Cell sorting analysis revealed that nuclear multi-lobulated cells were enriched in late S phase. Multi-lobulated nuclei were surrounded with lamin B1 that was particularly concentrated in concave regions of the nuclei. Furthermore, treatment with nocodazole or taxol disrupted multi-lobulation of the nucleus. These results suggest that nuclear multi-lobulation in late S phase, which is dependent on polymerization and depolymerization of microtubules, may be involved in nuclear Chk-induced inhibition of proliferation.
Chk酪氨酸激酶使Src家族酪氨酸激酶磷酸化并抑制其激酶活性。我们最近发现Chk定位于细胞核以及细胞质中，并抑制细胞增殖。为了研究细胞核内Chk在增殖中的作用，构建并表达了各种Chk突变体。Chk的核定位诱导细胞核动态多叶化以及细胞周期S期延长。Chk的N端结构域及其激酶结构域的一部分而非激酶活性负责诱导多叶化。细胞分选分析显示，核多叶化细胞在S期晚期富集。多叶化细胞核被核纤层蛋白B1包围，核纤层蛋白B1特别集中在细胞核的凹陷区域。此外，用诺考达唑或紫杉醇处理会破坏细胞核的多叶化。这些结果表明，S期晚期依赖于微管聚合和解聚的细胞核多叶化可能参与了核Chk诱导的增殖抑制。
