title: The ZO-1-associated Y-box factor ZONAB regulates epithelial cell proliferation and cell density.
abstract: 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.
authors.affiliation: Division of Cell Biology, Institute of Ophthalmology, University College London, London EC1V 9EL, UK. m.balda@ucl.ac.uk
authors.forename: Maria S
authors.initials: MS
authors.lastname: Balda
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Garrett
authors.forename: Karl
authors.initials: K
authors.lastname: Matter
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D002450:Cell Communication / Q000502:physiology*; D002455:Cell Division / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D051358:Cyclin-Dependent Kinase 4; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000172:deficiency* / Q000235:genetics; D004847:Epithelial Cells / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D011518:Proto-Oncogene Proteins; D016372:RNA, Antisense / Q000235:genetics; D011993:Recombinant Fusion Proteins; D015398:Signal Transduction / Q000502:physiology; D019108:Tight Junctions / Q000378:metabolism*; D014157:Transcription Factors / Q000172:deficiency* / Q000235:genetics; D062826:Zonula Occludens-1 Protein
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D016372:RNA, Antisense; D011993:Recombinant Fusion Proteins; C569042:TJP1 protein, human; D014157:Transcription Factors; C409302:ZONAB protein, Canis familiaris; D062826:Zonula Occludens-1 Protein; C495900:CDK4 protein, human; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases