Christine Dozier1, Mortaza Bonyadi1, Laurent Baricault1, Laure Tonasso1, Jean-Marie Darbon1
1Laboratoire de Biologie Cellulaire et Moléculaire du Contrôle de la Prolifération, UMR 5088 CNRS, Institut Fédératif de Recherche 109, Université Paul Sabatier, Bât 4R3-B1, 118 route de Narbonne, 31062 Toulouse, France.
Tóm tắt
Summry— Chk2 is a key player of the DNA damage signalling pathway. To identify new regulators of this kinase, we performed a yeast two‐hybrid screen and found that Chk2 associated with the B' regulatory subunit of protein phosphatase PP2A. In vitro GST‐Chk2 pulldowns demonstrated that B'γ isoforms bound to Chk2 with the strongest apparent affinity. This was confirmed in cellulo by co‐immunoprecipitation after overexpression of the respective partners in HEK293 cells. The A and C subunits of PP2A were present in the complexes, suggesting that Chk2 was associated with a functionnal PP2A. In vitro kinase assays showed that B'γ3 was a potent Chk2 substrate. This phosphorylation increased the catalytic phosphatase activity of PP2A measured on MAP kinase‐phosphorylated myelin basic protein as well as on autophosphorylated Chk2. Finally, we demonstrated that overexpressing B'γ3 in HEK293 suppressed the phosphorylation of Chk2 induced by a genotoxic treatment, suggesting that PP2A may counteract the action of the checkpoint kinase in living cells.
