Nuclear clusterin/XIP8, an x-ray-induced Ku70-binding protein that signals cell death

Yang, Chin-Rang; Leskov, Konstantin; Hosley-Eberlein, Kelly; Criswell, Tracy; Pink, John J.; Kinsella, Timothy J.; Boothman, David A.

Nuclear clusterin/XIP8, an x-ray-induced Ku70-binding protein that signals cell death

Authors

Yang, Chin-Rang

Leskov, Konstantin

Hosley-Eberlein, Kelly

Publisher

National Academy of Sciences

Description

Clusterin [CLU, a.k.a. TRPM-2, SGP-2, or ionizing radiation (IR)-induced protein-8 (XIP8)] was implicated in apoptosis, tissue injury, and aging. Its function remains elusive. We reisolated CLU/XIP8 by yeast two-hybrid analyses using as bait the DNA double-strand break repair protein Ku70. We show that a delayed (2–3 days), low-dose (0.02–10 Gy) IR-inducible nuclear CLU/XIP8 protein coimmunoprecipitated and colocalized (by confocal microscopy) in vivo with Ku70/Ku80, a DNA damage sensor and key double-strand break repair protein, in human MCF-7:WS8 breast cancer cells. Overexpression of nuclear CLU/XIP8 or its minimal Ku70 binding domain (120 aa of CLU/XIP8 C terminus) in nonirradiated MCF-7:WS8 cells dramatically reduced cell growth and colony-forming ability concomitant with increased G(1) cell cycle checkpoint arrest and increased cell death. Enhanced expression and accumulation of nuclear CLU/XIP8-Ku70/Ku80 complexes appears to be an important cell death signal after IR exposure.