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1 April 2005 Alterations of DNA Copy Number and Expression in Genes Involved in Cell Cycle Regulation and Apoptosis Signal Pathways in γ-Radiation-Sensitive SX9 Cells and -Resistant SR-1 Cells
Tomoyuki Koshikawa, Naoya Uematsu, Ayuko Iijima, Takuya Katagiri, Kazuhiko Uchida
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Abstract

Koshikawa, T., Uematsu, N., Iijima, A., Katagiri, T. and Uchida, K. Alterations of DNA Copy Number and Expression in Genes Involved in Cell Cycle Regulation and Apoptosis Signal Pathways in γ-Radiation-Sensitive SX9 Cells and -Resistant SR-1 Cells. Radiat. Res. 163, 374–383 (2005).

In the present study, genomic differences related to sensitivity to radiation were examined by comparative genomic hybridization and GeneChip 45K microarray in SX9 cells (radiation-sensitive) and their parental line, SR-1 (radiation-resistant). SX9 cells have defective DNA-dependent protein kinase catalytic subunit (DNA-PKcs) activity. DNA-PKcs is a DNA double-strand break repair protein that maintains chromosomal stability through nonhomologous end joining. However, the molecular basis of the radiation sensitivity of SX9 cells is unclear. Flow cytometry analysis showed that SR-1 and SX9 cells had a larger G2/M-phase population at 12 h after 4 Gy γ irradiation, while only SR-1 cells progressed to G1/S at 24–36 h. SX9 and SR-1 cells had similar patterns of DNA copy number alteration, but the gains were observed on chromosome 9 (cent-E2), 11 (cent-A3), and 12 (C1-E) only in SX9 cells. Expression of genes located on those regions is higher in SX-9 cells than in SR1 cells, and the regions include genes associated with apoptosis and cell cycle regulation. Time-course data for gene expression at 0, 1, 3, 6 and 12 h after 4 Gy γ irradiation revealed that the genes whose expression was altered in SX9 cells but not in SR-1 cells are in 16 clusters. Three of these clusters included genes for cell cycle regulation: JNK, PKC (PRKC) and ceramide cascade protein. These results suggest that amplification and altered expression of genes associated with cell cycle and apoptosis regulators in DNA-PK-deficient SX9 cells affect the differences in response to γ radiation between SX9 and SR-1 cells.

Tomoyuki Koshikawa, Naoya Uematsu, Ayuko Iijima, Takuya Katagiri, and Kazuhiko Uchida "Alterations of DNA Copy Number and Expression in Genes Involved in Cell Cycle Regulation and Apoptosis Signal Pathways in γ-Radiation-Sensitive SX9 Cells and -Resistant SR-1 Cells," Radiation Research 163(4), 374-383, (1 April 2005). https://doi.org/10.1667/RR3332
Received: 23 July 2004; Accepted: 1 November 2004; Published: 1 April 2005
JOURNAL ARTICLE
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