21. Expression, Subcellular Localization and Chromosome Localization of Hamster Ku70 and Ku80

Manabu Koike, Asato Kuroiwa*, Yoichi Matsuda* and Aki Koike.
(*Hokkaido Univ.)

Keywords: Ku70, Ku80, hamster, mapping, GFP

Ku, a heterodimer of Ku70 and Ku80, plays a key role in multiple nuclear processes, e.g. DNA repair, chromosome maintenance, and transcription regulation. To understand the fundamental characteristics of Ku proteins, we examined the electrophoretic mobility, subcellular localization and expression of hamster Ku70 and Ku80 and determined the chromosome locations of their genes. When transfected into hamster cells, exogenous Ku70 and Ku80 tagged with green fluorescent protein (GFP) accumulated in the nucleus, indicating that both Ku proteins can localize in the nucleus of hamster cells. The electrophoretic mobility of hamster Ku proteins is different from that of human Ku proteins. No significant changes in the quantity of Ku proteins were observed in CHO-K1 cells treated with 10 Gy of ionizing radiation, suggesting that both proteins are expressed constitutively in amounts adequate to repair DNA DSBs. The chromosome locations of the Ku genes were determined by direct R-banding fluorescence in situ hybridization. The Ku70 gene was localized to Syrian hamster chromosome 4qa4.1 qa4.2 and Chinese hamster chromosome 2p3.1, and the Ku80 gene was localized to Syrian hamster chromosome 4qb5 qb6.1 and Chinese hamster chromosome 2p3.5 p3.6. These results provide clues to the biological functions of Ku, as well as useful information for constructing comparative chromosome maps between hamsters and other mammalian species, including human, mouse, and rat.

Publications:
1) Koike, M., Kuroiwa, A., Koike, A., Shiomi, T., and Matsuda, Y. : Cytogenetics and Cell Genetics. 93, 52-56, 2001.
2) Koike, M., Shiomi, T., and Koike, A.: J. Biol. Chem. 276, 11167-11173, 2001.