Expression and distribution of symplekin regulates the assembly and function of the epithelial tight junction.
ABSTRACT Symplekin is multifunctional protein localized to both the tight junction and the nucleus with known roles in mRNA polyadenylation, proliferation, differentiation and tumorigenesis. Functions of symplekin at tight junctions have not been systematically investigated. In this study, increased expression of symplekin was observed during the formation of tight junctions in cultured HT-29 and HepG2 epithelial cells. Repression of symplekin by RNAi increased the permeability of epithelial monolayers, disrupted cellular polarity, and decreased the expression of the tight junction protein ZO-1. Moreover, symplekin was co-localized with ZO-1 at tight junctions and co-immunoprecipitated with ZO-1, indicating that ZO-1 and symplekin form complexes. In conclusion, symplekin expression regulates the assembly of tight junctions, thus helps to maintain the integrity of the epithelial monolayer and cellular polarity.
SourceAvailable from: Jérôme Paggetti[Show abstract] [Hide abstract]
ABSTRACT: MOZ and MLL encoding a histone acetyltransferase and a histone methyltransferase, respectively, are targets for recurrent chromosomal translocations found in acute myeloblastic or lymphoblastic leukemia. We have previously shown that MOZ and MLL cooperate to activate HOXA9 gene expression in hematopoietic stem/progenitors cells. To dissect the mechanism of action of this complex, we decided to identify new proteins interacting with MOZ. We found that the scaffold protein Symplekin that supports the assembly of polyadenylation machinery was identified by mass spectrometry. Symplekin interacts and co-localizes with both MOZ and MLL in immature hematopoietic cells. Its inhibition leads to a decrease of HOXA9 protein level but not of Hoxa9 mRNA and to an over-recruitment of MOZ and MLL onto HOXA9 promoter. Altogether, our results highlight the role of Symplekin in transcription repression involving a regulatory network between MOZ, MLL and Symplekin.Biochimica et Biophysica Acta 08/2013; 1833(12). DOI:10.1016/j.bbamcr.2013.08.013 · 4.66 Impact Factor
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ABSTRACT: Background Epithelial junctions and mucins compose a major portion of the mucosal barrier. Helicobacter pylori (H. pylori) infections induce alterations of the tight junctions and adherens junctions in epithelial cells, although the precise mechanisms underlying this process are not fully understood.Methods The expression of adhesion molecules and MUC1 was systematically investigated in gastrointestinal epithelial cells infected with H. pylori in vitro and in vivo. Furthermore, we developed several new in vitro methods to study the relationships between the bacterium and the dysfunction of tight junctions using Boyden Chambers.ResultsThe expression of a series of junctional molecules and MUC1 decreased in the cultured cells that were infected with H. pylori. According to the degree of damage at the tight junctions, direct contact of H. pylori with the apical membrane of the cells resulted in the greatest increase in permeability compared to basal membrane binding or non-binding of H. pylori to the cells. Similarly, we noted that H. pylori infection could reduce the expression and glycosylation of MUC1.Conclusions Helicobacter pylori dwelling on the apical surface of the gastrointestinal epithelium could directly induce serious injury of the mucosal barrier, and the new methods outlined here, based on the Boyden Chamber system, could be very useful for studying the relationships between bacteria and their target cells.Helicobacter 05/2014; DOI:10.1111/hel.12138 · 2.99 Impact Factor
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ABSTRACT: Although tumor invasion and metastasis are both classical hallmarks of cancer malignancy and the major causes of poor clinical outcomes among cancer patients, the underlying master regulators of invasion and metastasis remain largely unknown. In this study, we observed that an overexpression of microspherule protein 1 (MCRS1) promotes the invasion and metastasis of non-small cell lung cancer (NSCLC) cells. Furthermore, we sought to systematically investigate the pathophysiological functions and related mechanisms of MCRS1.Molecular Cancer 11/2014; 13(1):245. DOI:10.1186/1476-4598-13-245 · 5.40 Impact Factor