Arkadia Enhances Nodal/TGF-β Signaling by Coupling Phospho-Smad2/3 Activity and Turnover. - Mavrakis, Konstantinos J.; Andrew, Rebecca L.; Kian Leong Lee; Petropoulou, Chariklia; Dixon, James E.; Navaratnam, Naveenan; Norris, Dominic P.; Episkopou, Vasso (PLoS Biology, 2007)