| Binding of GEF H 1 to the tight junction associated adaptor cingulin results in inhibition of Rho signaling and G1 / S phase transition . ^^^ In agreement , RNA interference of GEF H 1 or transfection of GEF H 1 binding cingulin mutants inhibit G1 / S phase transition of MDCK cells , and depletion of cingulin by regulated RNA interference results in irregular monolayers and RhoA activation . ^^^ These results indicate that forming epithelial tight junctions contribute to the downregulation of RhoA in epithelia by inactivating GEF H 1 in a cingulin dependent manner , providing a molecular mechanism whereby tight junction formation is linked to inhibition of RhoA signaling . . ^^^ |