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. 2011 May 15;22(10):1677–1685. doi: 10.1091/mbc.E10-08-0677

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© 2011 Capaldo et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

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FIGURE 7: — ZO-3–cyclin D1 interaction regulates cell proliferation in epithelial cells by promoting S-phase transition. (A) Western blot analysis of SKCO-15 cell lysates treated with control siRNA (Control) or ZO-3 directed siRNA. (B) Growth curve showing cell number over 3 d posttransfection with control siRNA (Control, ◊) or ZO-3 directed siRNA (▪) (*p < 0.001, n = 4). (C) Propidium iodide–stained SKCO-15 cells, treated with either scrambled siRNA (Control, black) or ZO-3–directed siRNA (red) were assayed for cell-cycle status by flow cytometry (n = 2). (D) Confluent SKCO-15 cell monolayers (control) were scratch wounded to stimulate cell proliferation (dotted line marks wound edge; mitotic cells are marked with white arrows). Scale bar = 20 μm. (E) Scratch-wounded monolayers show increased cyclin D1 as well as increased phospho-Thr-286–cyclin D1 when compared with confluent cultures (control). (F) Western blot showing enhanced ZO-3 coimmunoprecipitation with cyclin D1 from lysates of scratch-wounded cells. (G) Hypothetical model whereby ZO-3 acts to sequester cyclin D1 at TJs during mitosis. This prevents cyclin D1 degradation during M-phase and promotes S-phase transition. Without ZO-3, cyclin D1 is degraded during M-phase, delaying cells in G₁.