1. Heat shock protein 90α (HSP90α), a substrate and chaperone of DNA-PK necessary for the apoptotic response
- Author
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Leonard M. Neckers, Kurt W. Kohn, Jane B. Trepel, Yves Pommier, Wanping Xu, Stéphanie Solier, and Bradley T. Scroggins
- Subjects
DNA repair ,DNA damage ,Blotting, Western ,Apoptosis ,DNA Fragmentation ,DNA-Activated Protein Kinase ,environment and public health ,Histones ,TNF-Related Apoptosis-Inducing Ligand ,chemistry.chemical_compound ,Cell Line, Tumor ,Commentaries ,Heat shock protein ,In Situ Nick-End Labeling ,Humans ,Fluorometry ,HSP90 Heat-Shock Proteins ,Phosphorylation ,RNA, Small Interfering ,Multidisciplinary ,biology ,Geldanamycin ,Flow Cytometry ,Apoptotic body ,Hsp90 ,MDC1 ,Cell biology ,Enzyme Activation ,enzymes and coenzymes (carbohydrates) ,Microscopy, Fluorescence ,chemistry ,biology.protein ,DNA fragmentation - Abstract
The “apoptotic ring” is characterized by the phosphorylation of histone H2AX at serine 139 (γ-H2AX) by DNA-dependent protein kinase (DNA-PK). The γ-H2AX apoptotic ring differs from the nuclear foci patterns observed in response to DNA-damaging agents. It contains phosphorylated DNA damage response proteins including activated Chk2, activated ATM, and activated DNA-PK itself but lacks MDC1 and 53BP1, which are required to initiate DNA repair. Because DNA-PK can phosphorylate heat shock protein 90α (HSP90α) in biochemical assays, we investigated whether HSP90α is involved in the apoptotic ring. Here we show that HSP90α is phosphorylated by DNA-PK on threonines 5 and 7 early during apoptosis and that both phosphorylated HSP90α and DNA-PK colocalize in the apoptotic ring. We also show that DNA-PK is a client of HSP90α and that HSP90α is required for full DNA-PK activation, γ-H2AX formation, DNA fragmentation, and apoptotic body formation. In contrast, HSP90 inhibition by geldanamycin markedly enhances TRAIL-induced DNA-PK and H2AX activation. Together, our results reveal that HSP90α is a substrate and chaperone of DNA-PK in the apoptotic response. The response of phosphorylated HSP90α to TRAIL and its localization to the γ-H2AX ring represent epigenetic features of apoptosis that offer insights for studying and monitoring nuclear apoptosis.
- Published
- 2012