Balda Maria S, Garrett Michelle D, Matter Karl
Division of Cell Biology, Institute of Ophthalmology, University College London, London EC1V 9EL, UK.
J Cell Biol. 2003 Feb 3;160(3):423-32. doi: 10.1083/jcb.200210020.
Epithelial tight junctions regulate paracellular permeability, restrict apical/basolateral intramembrane diffusion of lipids, and have been proposed to participate in the control of epithelial cell proliferation and differentiation. Previously, we have identified ZO-1-associated nucleic acid binding proteins (ZONAB), a Y-box transcription factor whose nuclear localization and transcriptional activity is regulated by the tight junction-associated candidate tumor suppressor ZO-1. Now, we found that reduction of ZONAB expression using an antisense approach or by RNA interference strongly reduced proliferation of MDCK cells. Transfection of wild-type or ZONAB-binding fragments of ZO-1 reduced proliferation as well as nuclear ZONAB pools, indicating that promotion of proliferation by ZONAB requires its nuclear accumulation. Overexpression of ZONAB resulted in increased cell density in mature monolayers, and depletion of ZONAB or overexpression of ZO-1 reduced cell density. ZONAB was found to associate with cell division kinase (CDK) 4, and reduction of nuclear ZONAB levels resulted in reduced nuclear CDK4. Thus, our data indicate that tight junctions can regulate epithelial cell proliferation and cell density via a ZONAB/ZO-1-based pathway. Although this regulatory process may also involve regulation of transcription by ZONAB, our data suggest that one mechanism by which ZONAB and ZO-1 influence proliferation is by regulating the nuclear accumulation of CDK4.
上皮紧密连接调节细胞旁通透性，限制脂质在顶端/基底外侧膜内的扩散，并被认为参与上皮细胞增殖和分化的控制。此前，我们已鉴定出与闭锁小带蛋白1（ZO-1）相关的核酸结合蛋白（ZONAB），一种Y盒转录因子，其核定位和转录活性受紧密连接相关候选肿瘤抑制因子ZO-1的调节。现在，我们发现采用反义方法或RNA干扰降低ZONAB表达可显著降低MDCK细胞的增殖。转染野生型或ZO-1的ZONAB结合片段可降低增殖以及核内ZONAB的量，表明ZONAB促进增殖需要其核内积累。ZONAB过表达导致成熟单层细胞密度增加，而ZONAB缺失或ZO-1过表达则降低细胞密度。发现ZONAB与细胞分裂激酶（CDK）4相关，核内ZONAB水平降低导致核内CDK4减少。因此，我们的数据表明紧密连接可通过基于ZONAB/ZO-1的途径调节上皮细胞增殖和细胞密度。尽管这一调节过程可能还涉及ZONAB对转录的调节，但我们的数据表明ZONAB和ZO-1影响增殖的一种机制是通过调节CDK4的核内积累。
