title: Heat shock protein 90α (HSP90α), a substrate and chaperone of DNA-PK necessary for the apoptotic response.
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.
authors: Laboratory of Molecular Pharmacology, Urologic Oncology Branch, and Medical Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA.
authors: Stéphanie
authors: S
authors: Solier
authors: Kurt W
authors: KW
authors: Kohn
authors: Bradley
authors: B
authors: Scroggins
authors: Wanping
authors: W
authors: Xu
authors: Jane
authors: J
authors: Trepel
authors: Leonard
authors: L
authors: Neckers
authors: Yves
authors: Y
authors: Pommier
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D053938:DNA Fragmentation; D051747:DNA-Activated Protein Kinase / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000502:physiology; D005434:Flow Cytometry; D005470:Fluorometry; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D006801:Humans; D020287:In Situ Nick-End Labeling; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000235:genetics; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism
chemical_list: C468783:H2AX protein, human; D018841:HSP90 Heat-Shock Proteins; D006657:Histones; D034741:RNA, Small Interfering; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D051747:DNA-Activated Protein Kinase