B56γ-PP2A mediates dephosphorylation of CREB and ATF1.

(A) Okadaic acid (OA) sensitivity. HEK 293T cells were left untreated or exposed to 10 nM and 100 nM OA for 1 h. They were then subjected to IR for the indicated times. Cell extracts were prepared and analyzed by immunoblotting with α-CREB, α-pCREB-108/111/114 and α-pCREB-121 antibodies. (B) PP2Ac knockdown stimulates DNA damage-dependent CREB phosphorylation. HEK 293T cells expressing an shRNA targeting PP2Ac were compared to cells expressing a non-targeting shRNA construct. Cells were exposed to 10 Gy IR for 2 h and subjected to immunoblotting analysis with α-CREB, α-pCREB-108/111/114, α-pCREB-121 and α-PP2Ac antibodies. (C) B56γ knockdown stimulates DNA damage-dependent CREB phosphorylation. HEK 293T cells expressing an shRNA targeting B56γ were compared to cells expressing a non-targeting shRNA construct. Cells were exposed to 10 Gy IR for 1 h and subjected to immunoblotting analysis with α-CREB, α-pCREB-108/111/114, α-pCREB-121 and α-B56γ antibodies. (D) Effects of B56γ knockdown on ATF1 Ser-47/50/51 phosphorylation. HEK 293T cells were transiently transfected with control or B56γ siRNA and the levels of ATF1 Ser-47/50/51 phosphorylation assessed using α-pATF1-47/50/51 antibodies.