TY - JOUR
T1 - The BARD1 BRCT domain contributes to p53 binding, cytoplasmic and mitochondrial localization, and apoptotic function
AU - Tembe, Varsha
AU - Martino-Echarri, Estefania
AU - Marzec, Kamila A.
AU - Mok, Myth T S
AU - Brodie, Kirsty M.
AU - Mills, Kate
AU - Lei, Ying
AU - DeFazio, Anna
AU - Rizos, Helen
AU - Kettle, Emma
AU - Boadle, Ross
AU - Henderson, Beric R.
PY - 2015/9/1
Y1 - 2015/9/1
N2 - BARD1 is a breast cancer tumor suppressor with multiple domains and functions. BARD1 comprises a tandem BRCT domain at the C-terminus, and this sequence has been reported to target BARD1 to distinct subcellular locations such as nuclear DNA breakage sites and the centrosome through binding to regulatory proteins such as HP1 and OLA1, respectively. We now identify the BRCT domain as a binding site for p53. We first confirmed previous reports that endogenous BARD1 binds to p53 by immunoprecipitation assay, and further show that BARD1/p53 complexes locate at mitochondria suggesting a cellular location for p53 regulation of BARD1 apoptotic activity. We used a proximity ligation assay to map three distinct p53 binding sequences in human BARD1, ranging from weak (425-525) and modest (525-567) to strong (551-777 comprising BRCT domains). Deletion of the BRCT sequence caused major defects in the ability of BARD1 to (1) bind p53, (2) localize to the cytoplasm and mitochondria, and (3) induce Bax oligomerization and apoptosis. Our data suggest that BARD1 can move to mitochondria independent of p53, but subsequently associates with p53 to induce Bax clustering in part by decreasing mitochondrial Bcl-2 levels. We therefore identify a role for the BRCT domain in stimulating BARD1 nuclear export and mitochondrial localization, and in assembling mitochondrial BARD1/p53 complexes to regulate specific activities such as apoptotic function.
AB - BARD1 is a breast cancer tumor suppressor with multiple domains and functions. BARD1 comprises a tandem BRCT domain at the C-terminus, and this sequence has been reported to target BARD1 to distinct subcellular locations such as nuclear DNA breakage sites and the centrosome through binding to regulatory proteins such as HP1 and OLA1, respectively. We now identify the BRCT domain as a binding site for p53. We first confirmed previous reports that endogenous BARD1 binds to p53 by immunoprecipitation assay, and further show that BARD1/p53 complexes locate at mitochondria suggesting a cellular location for p53 regulation of BARD1 apoptotic activity. We used a proximity ligation assay to map three distinct p53 binding sequences in human BARD1, ranging from weak (425-525) and modest (525-567) to strong (551-777 comprising BRCT domains). Deletion of the BRCT sequence caused major defects in the ability of BARD1 to (1) bind p53, (2) localize to the cytoplasm and mitochondria, and (3) induce Bax oligomerization and apoptosis. Our data suggest that BARD1 can move to mitochondria independent of p53, but subsequently associates with p53 to induce Bax clustering in part by decreasing mitochondrial Bcl-2 levels. We therefore identify a role for the BRCT domain in stimulating BARD1 nuclear export and mitochondrial localization, and in assembling mitochondrial BARD1/p53 complexes to regulate specific activities such as apoptotic function.
UR - http://www.scopus.com/inward/record.url?scp=84930616638&partnerID=8YFLogxK
U2 - 10.1016/j.cellsig.2015.05.011
DO - 10.1016/j.cellsig.2015.05.011
M3 - Article
C2 - 26022179
AN - SCOPUS:84930616638
SN - 0898-6568
VL - 27
SP - 1763
EP - 1771
JO - Cellular Signalling
JF - Cellular Signalling
IS - 9
ER -