Role for proteasome activator PA200 and postglutamyl proteasome activity in genomic stability.
Proteasome activator PA200 enhances proteasome-mediated cleavage after acidic residues in vitro; however, its role within cells is not known. Here, we show that, in response to ionizing radiation, PA200 forms hybrid proteasomes with 19S caps and 20S core proteasomes that accumulate on chromatin, leading to an increase in proteolytic activity. Unlike many other proteins that respond to DNA damage, the response of PA200 appears to be independent of Ataxia Telangiectasia Mutated and p53, but dependent on DNA-dependent protein kinase activity. Nonetheless, PA200 is critical because PA200-knockdown cells show genomic instability and reduced survival after exposure to ionizing radiation. This phenotype is reproduced by specific inhibition of postglutamyl activity of proteasomes, but combined treatment with PA200 siRNA and postglutamyl inhibitor does not show additive effects on survival. Together, these data suggest a unique role for PA200 in genomic stability that is likely mediated through its ability to enhance postglutamyl cleavage by proteasomes.
Department of Immunology, Roswell Park Cancer Institute, Buffalo, NY 14263.
Jennifer
J
Blickwedehl
Manjula
M
Agarwal
Changhyun
C
Seong
Raj K
RK
Pandita
Thomas
T
Melendy
Patrick
P
Sung
Tej K
TK
Pandita
Naveen
N
Bangia
D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival; D002843:Chromatin / Q000235:genetics; D006224:Cricetinae; D051747:DNA-Activated Protein Kinase / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D042822:Genomic Instability / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D005973:Glutamine / Q000378:metabolism; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D061988:Proteasome Inhibitors; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D005973:Glutamine; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase; D017346:Protein Serine-Threonine Kinases; D046988:Proteasome Endopeptidase Complex