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Updated: Jun 27, 2026

Analysis of Cell Cycle Position in Mammalian Cells
Published on: January 21, 2012
Zona occludens-2 inhibits cyclin D1 expression and cell proliferation and exhibits changes in localization along the
Rocio Tapia1, Miriam Huerta, Socorro Islas
1Department of Physiology, Biophysics, and Neuroscience, Center for Research and Advanced Studies (CINVESTAV), Mexico, D.F., 07360, Mexico.
Abstract:
Here, we have studied the effect of the tight junction protein zona occludens (ZO)-2 on cyclin D1 (CD1) protein expression. CD1 is essential for cell progression through the G1 phase of the cell cycle. We have found that in cultures of synchronized Madin-Darby canine kidney cells, ZO-2 inhibits cell proliferation at G0/G1 and decreases CD1 protein level. These effects occur in response to a diminished CD1 translation and an augmented CD1 degradation at the proteosome triggered by ZO-2. ZO-2 overexpression decreases the amount of Glycogen synthase kinase-3beta phosphorylated at Ser9 and represses beta-catenin target gene expression. We have also explored the expression of ZO-2 through the cell cycle and demonstrate that ZO-2 enters the nucleus at the late G1 phase and leaves the nucleus when the cell is in mitosis. These results thus explain why in confluent quiescent epithelia ZO-2 is absent from the nucleus and localizes at the cellular borders, whereas in sparse proliferating cultures ZO-2 is conspicuously present at the nucleus.
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