RelA suppresses the Wnt/beta-catenin pathway without exerting trans-acting transcriptional ability.

Several cellular signaling systems exhibit cross talk. Cross talk seems to play an important role in modifying signal effects. In vertebrates, the nuclear factor kappa B (NF-kappaB) signaling pathway plays important roles in immune response, inflammation and apoptosis. Meanwhile, the Wnt/beta-catenin signaling pathway is involved in oncogenesis and development. We show here that RelA, a component of NF-kappaB, specifically suppressed beta-catenin/Tcf-dependent transcription. This suppression did not depend on the trans-acting transcriptional ability of RelA. Furthermore, RelA neither affected the nuclear import of beta-catenin nor the DNA binding ability of the beta-catenin/Tcf complex, suggesting that NF-kappaB modifies this signaling pathway after the binding of the beta-catenin/Tcf complex with target DNA.