TCF7 in p21 pathway. Different isoforms of TCF7 plays totally different role in p21 pathway. The active TCF, includes the full-length TCF7 isoform, down-regulates p21, which may inhibits the cyclinB/cdc2 induced G2 to M phase transition. The β-catenin/TCF mediated cell cycle stall at G2 phase can be repressed by N-cadherin. Conversely, the negative isoform of TCF7, one of which is known as dnTCF1E, inhibits the p21 repressor genes, thus induces p21 expression, and arrests the cell cycle at G1 phase through inhibition of cyclinE/cdk2 complex. TCF T cell factor, dnTCF1E dominant negative E-tail isoform of TCF1.