KARP-1 works as a heterodimer with Ku70, but the function of KARP-1 cannot perfectly replace that of Ku80 in DSB repair

Journal Article · Sat Oct 01 04:00:00 EDT 2011 · Experimental Cell Research

DOI:https://doi.org/10.1016/J.YEXCR.2011.06.015· OSTI ID:22212174

Koike, Manabu ^[1]; Yutoku, Yasutomo ^[1]; Koike, Aki ^[1]

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1. DNA Repair Gene Research, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)

Ku, the heterodimer of Ku70 and Ku80, plays an essential role in the DNA double-strand break (DSB) repair pathway, i.e., non-homologous end-joining (NHEJ). Two isoforms of Ku80 encoded by the same genes, namely, Ku80 and KARP-1 are expressed and function in primate cells, but not in rodent cells. Ku80 works as a heterodimer with Ku70. However, it is not yet clear whether KARP-1 forms a heterodimer with Ku70 and works as a heterodimer. Although KARP-1 appears to work in NHEJ, its physiological role remains unclear. In this study, we established and characterized EGFP-KARP-1-expressing xrs-6 cell lines, EGFP-KARP-1/xrs-6. We found that nuclear localization signal (NLS) of KARP-1 is localized in the C-terminal region. Our data showed that KARP-1 localizes within the nucleus in NLS-dependent and NLS-independent manner and forms a heterodimer with Ku70, and stabilizes Ku70. On the other hand, EGFP-KARP-1 could not perfectly complement the radiosensitivity and DSB repair activity of Ku80-deficient xrs-6 cells. Furthermore, KARP-1 could not accumulate at DSBs faster than Ku80, although EGFP-KARP-1 accumulates at DSBs. Our data demonstrate that the function of KARP-1 could not perfectly replace that of Ku80 in DSB repair, although KARP-1 has some biochemical properties, which resemble those of Ku80, and works as a heterodimer with Ku70. On the other hand, the number of EGFP-KARP-1-expressing xrs-6 cells showing pan-nuclear {gamma}-H2AX staining significantly increases following X-irradiation, suggesting that KARP-1 may have a novel role in DSB response.

• OSTI ID: 22212174
• Journal Information: Experimental Cell Research, Journal Name: Experimental Cell Research Journal Issue: 16 Vol. 317; ISSN 0014-4827; ISSN ECREAL
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
BIOLOGICAL PATHWAYS
DNA
DNA REPAIR
GENES
IRRADIATION
STRAND BREAKS