Granzyme A, which causes single-stranded DNA damage, targets the double-strand break repair protein Ku70.
Granzyme A (GzmA) induces caspase-independent cell death with morphological features of apoptosis. Here, we show that GzmA at nanomolar concentrations cleaves Ku70, a key double-strand break repair (DSBR) protein, in target cells. Ku70 is cut after Arg(301), disrupting Ku complex binding to DNA. Cleaving Ku70 facilitates GzmA-mediated cell death, as silencing Ku70 by RNA interference increases DNA damage and cell death by GzmB cluster-deficient cytotoxic T lymphocytes or by GzmA and perforin, whereas Ku70 overexpression has the opposite effect. Ku70 has two known antiapoptotic effects-facilitating DSBR and sequestering bax to prevent its translocation to mitochondria. However, GzmA triggers single-stranded, not double-stranded, DNA damage, and GzmA-induced cell death does not involve bax. Therefore, Ku70 has other antiapoptotic functions in GzmA-induced cell death, which are blocked when GzmA proteolyses Ku70.
Zhu
Pengcheng
P
The CBR Institute for Biomedical Research and Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Zhang
Dong
D
Chowdhury
Dipanjan
D
Martinvalet
Denis
D
Keefe
Dennis
D
Shi
Lianfa
L
Lieberman
Judy
J
D000818:Animals; D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism*; D001120:Arginine / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage / Q000187:drug effects; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D053804:Granzymes; D006801:Humans; D000072200:Ku Autoantigen; D008562:Membrane Glycoproteins / Q000494:pharmacology; D051379:Mice; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D011480:Protease Inhibitors / Q000494:pharmacology; D011485:Protein Binding; D012697:Serine Endopeptidases / Q000378:metabolism* / Q000494:pharmacology; D013602:T-Lymphocytes, Cytotoxic / Q000378:metabolism
D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D011480:Protease Inhibitors; D054353:Perforin; D004247:DNA; D001120:Arginine; D053804:Granzymes; D012697:Serine Endopeptidases; C509212:GZMA protein, human; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen