Role of Ku70 in deubiquitination of Mcl-1 and suppression of apoptosis.
Mcl-1 is a unique antiapoptotic Bcl2 family member with a short half-life due to its rapid turnover through ubiquitination. We discovered that Ku70, a DNA double-strand break repair protein, functions as a deubiquitinase to stabilize Mcl-1. Ku70 knockout in mouse embryonic fibroblast (MEF) cells or depletion from human lung cancer H1299 cells leads to the accumulation of polyubiquitinated Mcl-1 and a reduction in its half-life and protein expression. Conversely, expression of exogenous Ku70 in Ku70(-/-) MEF cells restores Mcl-1 expression. Subcellular fractionation indicates that Ku70 extensively colocalizes with Mcl-1 in mitochondria, endoplasmic reticulum and nucleus in H1299 cells. Ku70 directly interacts with Mcl-1 via its C terminus (that is, aa 536-609), which is required and sufficient for deubiquitination and stabilization of Mcl-1, leading to suppression of apoptosis. Purified Ku70 protein directly deubiquitinates Mcl-1 by removing K48-linked polyubiquitin chains. Ku70 knockdown not only promotes Mcl-1 turnover but also enhances antitumor efficacy of the BH3-mimetic ABT-737 in human lung cancer xenografts. These findings identify Ku70 as a novel Mcl-1 deubiquitinase that could be a potential target for cancer therapy by manipulating Mcl-1 deubiquitination.
Division of Cancer Biology, Department of Radiation Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA.
B
B
Wang
Division of Cancer Biology, Department of Radiation Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA.
M
M
Xie
Division of Cancer Biology, Department of Radiation Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA.
R
R
Li
Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA.
T K
TK
Owonikoko
Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA.
S S
SS
Ramalingam
Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA.
F R
FR
Khuri
Division of Cancer Biology, Department of Radiation Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA.
W J
WJ
Curran
Division of Cancer Biology, Department of Radiation Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA.
Y
Y
Wang
Division of Cancer Biology, Department of Radiation Oncology, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA.
X
X
Deng
D000818:Animals; D034961:Antigens, Nuclear / Q000502:physiology*; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D001713:Biphenyl Compounds / Q000494:pharmacology; D002470:Cell Survival; D004268:DNA-Binding Proteins / Q000502:physiology*; D045325:HCT116 Cells; D057809:HEK293 Cells; D006207:Half-Life; D006801:Humans; D000072200:Ku Autoantigen; D051379:Mice; D008819:Mice, Nude; D064549:Myeloid Cell Leukemia Sequence 1 Protein / Q000378:metabolism*; D009596:Nitrophenols / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D054730:Protein Interaction Domains and Motifs; D055550:Protein Stability; D021381:Protein Transport; D019311:Staurosporine / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D054875:Ubiquitination; D023041:Xenograft Model Antitumor Assays
C501332:ABT-737; D034961:Antigens, Nuclear; D000970:Antineoplastic Agents; D001713:Biphenyl Compounds; D004268:DNA-Binding Proteins; C579095:MCL1 protein, human; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009596:Nitrophenols; D010879:Piperazines; D013449:Sulfonamides; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen; D019311:Staurosporine