title: ZO proteins redundantly regulate the transcription factor DbpA/ZONAB.
abstract: The localization and activities of DbpA/ZONAB and YAP transcription factors are in part regulated by the density-dependent assembly of epithelial junctions. DbpA activity and cell proliferation are inhibited by exogenous overexpression of the tight junction (TJ) protein ZO-1, leading to a model whereby ZO-1 acts by sequestering DbpA at the TJ. However, mammary epithelial cells and mouse tissues knock-out for ZO-1 do not show increased proliferation, as predicted by this model. To address this discrepancy, we examined the localization and activity of DbpA and YAP in Madin-Darby canine kidney cells depleted either of ZO-1, or one of the related proteins ZO-2 and ZO-3 (ZO proteins), or all three together. Depletion of only one ZO protein had no effect on DbpA localization and activity, whereas depletion of ZO-1 and ZO-2, which is associated with reduced ZO-3 expression, resulted in increased DbpA localization in the cytoplasm. Only depletion of ZO-2 reduced the nuclear import of YAP. Mammary epithelial (Eph4) cells KO for ZO-1 showed junctional DbpA, demonstrating that ZO-1 is not required to sequester DbpA at junctions. However, further depletion of ZO-2 in Eph4 ZO-1KO cells, which do not express ZO-3, caused decreased junctional localization and expression of DbpA, which were rescued by the proteasome inhibitor MG132. In vitro binding assays showed that full-length ZO-1 does not interact with DbpA. These results show that ZO-2 is implicated in regulating the nuclear shuttling of YAP, whereas ZO proteins redundantly control the junctional retention and stability of DbpA, without affecting its shuttling to the nucleus.
authors.affiliation: From the Department of Cell Biology, University of Geneva, 1211 Geneva, Switzerland.
authors.forename: Domenica
authors.initials: D
authors.lastname: Spadaro
authors.affiliation: From the Department of Cell Biology, University of Geneva, 1211 Geneva, Switzerland.
authors.forename: Rocio
authors.initials: R
authors.lastname: Tapia
authors.affiliation: From the Department of Cell Biology, University of Geneva, 1211 Geneva, Switzerland.
authors.forename: Lionel
authors.initials: L
authors.lastname: Jond
authors.affiliation: the Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822, the Department of Medicine/Nephrology, Mount Sinai Medical School, New York, New York 10029, and.
authors.forename: Marius
authors.initials: M
authors.lastname: Sudol
authors.affiliation: the Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, North Carolina 27599.
authors.forename: Alan S
authors.initials: AS
authors.lastname: Fanning
authors.affiliation: From the Department of Cell Biology, University of Geneva, 1211 Geneva, Switzerland, sandra.citi@unige.ch.
authors.forename: Sandra
authors.initials: S
authors.lastname: Citi
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D018938:Caco-2 Cells; D002454:Cell Differentiation; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D006801:Humans; D007365:Intercellular Junctions / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism; D051379:Mice; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D062825:Zonula Occludens Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D062826:Zonula Occludens-1 Protein / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D062827:Zonula Occludens-2 Protein / Q000172:deficiency / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; C569043:Tjp1 protein, mouse; C569047:Tjp2 protein, mouse; C491774:Tjp3 protein, mouse; D014157:Transcription Factors; C409302:ZONAB protein, Canis familiaris; D062825:Zonula Occludens Proteins; D062826:Zonula Occludens-1 Protein; D062827:Zonula Occludens-2 Protein
keywords: Junction; Nucleus; Proliferation; Scaffold Protein; Transcription Factor