Zaidi Sayyed K, Young Daniel W, Pockwinse Shirwin M, Javed Amjad, Lian Jane B, Stein Janet L, van Wijnen Andre J, Stein Gary S
Department of Cell Biology and Cancer Center, University of Massachusetts Medical School, Worcester, MA 01655-0105, USA.
Proc Natl Acad Sci U S A. 2003 Dec 9;100(25):14852-7. doi: 10.1073/pnas.2533076100. Epub 2003 Dec 1.
Postmitotic gene expression requires restoration of nuclear organization and assembly of regulatory complexes. The hematopoietic and osteogenic Runx (Cbfa/AML) transcription factors are punctately organized in the interphase nucleus and provide a model for understanding the subnuclear organization of tissue-specific regulatory proteins after mitosis. Here we have used quantitative in situ immunofluorescence microscopy and quantitative image analysis to show that Runx factors undergo progressive changes in cellular localization during mitosis while retaining a punctate distribution. In comparison, the acetyl transferase p300 and acetylated histone H4 remain localized with DNA throughout mitosis while the RNA processing factor SC35 is excluded from mitotic chromatin. Subnuclear organization of Runx foci is completely restored in telophase, and Runx proteins are equally partitioned into progeny nuclei. In contrast, subnuclear organization of SC35 is restored subsequent to telophase. Our results show a sequential reorganization of Runx and its coregulatory proteins that precedes restoration of RNA processing speckles. Thus, mitotic partitioning and spatiotemporal reorganization of regulatory proteins together render progeny cells equivalently competent to support phenotypic gene expression.
有丝分裂后基因表达需要恢复核组织和调控复合物的组装。造血和成骨的Runx（Cbfa/AML）转录因子在间期核中呈点状分布，为理解有丝分裂后组织特异性调控蛋白的亚核组织提供了一个模型。在此，我们利用定量原位免疫荧光显微镜和定量图像分析表明，Runx因子在有丝分裂期间细胞定位发生渐进性变化，同时保持点状分布。相比之下，乙酰转移酶p300和乙酰化组蛋白H4在整个有丝分裂过程中都与DNA共定位，而RNA加工因子SC35被排除在有丝分裂染色质之外。Runx焦点的亚核组织在末期完全恢复，Runx蛋白被平均分配到子代核中。相反，SC35的亚核组织在末期之后恢复。我们的结果显示，在RNA加工斑点恢复之前，Runx及其共调控蛋白会进行顺序重组。因此，调控蛋白的有丝分裂分配和时空重组共同使子代细胞有同等能力支持表型基因表达。
