TY - JOUR
T1 - Breast cancer cell proliferation is inhibited by BAD
T2 - Regulation of cyclin D1
AU - Fernando, Romaine
AU - Foster, James S.
AU - Bible, Amber
AU - Ström, Anders
AU - Pestell, Richard G.
AU - Rao, Mahadev
AU - Saxton, Arnold
AU - Seung, Joon Baek
AU - Yamaguchi, Kiyoshi
AU - Donnell, Robert
AU - Cekanova, Maria
AU - Wimalasena, Jay
PY - 2007/9/28
Y1 - 2007/9/28
N2 - Recent investigations suggest that functions of the proapoptotic BCL2 family members, including BAD, are not limited to regulation of apoptosis. Here we demonstrate that BAD inhibits G1 to S phase transition in MCF7 breast cancer cells independent of apoptosis. BAD overexpression inhibited G1 transit and cell growth as well as cyclin D1 expression. Inhibition of cyclin D1 expression was mediated through inhibition of transcription activated by AP1. Chromatin immunoprecipitation assays indicated that BAD is localized at the 12-O-tetradecanoylphorbol-13-acetate-response element (TRE) and cAMP-response element (CRE) in the cyclin D1 promoter. This was shown to reflect direct binding interactions of BAD with c-Jun, and this interaction inhibited the activity of AP1 complexes at TRE. BAD did not interact with phosphorylated forms of c-Jun. Our data suggest that inhibitory TRE/CRE-c-Jun-BAD complexes are present at the cyclin D1 promoter in quiescent cells. Estrogen stimulation displaced BAD from TRE/CRE elements in MCF7 cells, whereas BAD overexpression inhibited estrogen-induced cyclin D1 synthesis and cell proliferation. Inhibition of endogenous BAD in MCF7 cells markedly increased the proliferative fraction and DNA synthesis, activated Cdks, and increased cyclin D1 protein levels. This action of BAD required serine residues Ser75 and Ser99. Both phosphorylated and unphosphorylated forms of BAD localized to the nuclei of human breast epithelial cells. Thus, we demonstrate a novel role for BAD in cell cycle regulation dependent upon its phosphorylation state and independent of the BAD/BCL2 interaction and apoptosis.
AB - Recent investigations suggest that functions of the proapoptotic BCL2 family members, including BAD, are not limited to regulation of apoptosis. Here we demonstrate that BAD inhibits G1 to S phase transition in MCF7 breast cancer cells independent of apoptosis. BAD overexpression inhibited G1 transit and cell growth as well as cyclin D1 expression. Inhibition of cyclin D1 expression was mediated through inhibition of transcription activated by AP1. Chromatin immunoprecipitation assays indicated that BAD is localized at the 12-O-tetradecanoylphorbol-13-acetate-response element (TRE) and cAMP-response element (CRE) in the cyclin D1 promoter. This was shown to reflect direct binding interactions of BAD with c-Jun, and this interaction inhibited the activity of AP1 complexes at TRE. BAD did not interact with phosphorylated forms of c-Jun. Our data suggest that inhibitory TRE/CRE-c-Jun-BAD complexes are present at the cyclin D1 promoter in quiescent cells. Estrogen stimulation displaced BAD from TRE/CRE elements in MCF7 cells, whereas BAD overexpression inhibited estrogen-induced cyclin D1 synthesis and cell proliferation. Inhibition of endogenous BAD in MCF7 cells markedly increased the proliferative fraction and DNA synthesis, activated Cdks, and increased cyclin D1 protein levels. This action of BAD required serine residues Ser75 and Ser99. Both phosphorylated and unphosphorylated forms of BAD localized to the nuclei of human breast epithelial cells. Thus, we demonstrate a novel role for BAD in cell cycle regulation dependent upon its phosphorylation state and independent of the BAD/BCL2 interaction and apoptosis.
UR - http://www.scopus.com/inward/record.url?scp=35349029694&partnerID=8YFLogxK
U2 - 10.1074/jbc.M700785200
DO - 10.1074/jbc.M700785200
M3 - Article
C2 - 17670745
AN - SCOPUS:35349029694
SN - 0021-9258
VL - 282
SP - 28864
EP - 28873
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 39
ER -