Differential gene expression in a DNA double-strand-break repair mutant XRS-5 defective in Ku80: analysis by cDNA microarray

• Published in: Journal of radiation research Vol. 42; no. 4; p. 371
• Main Authors: Chan, J Y, Chen, L K, Chang, J F, Ting, H M, Goy, C, Chen, J L, Hwang, J J, Chen, F D, Chen, D J, Ngo, F Q
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.12.2001
• Subjects: Analysis; Animals; Antigens, Nuclear; CHO Cells; Cricetinae; DNA; DNA Helicases; DNA Repair - genetics; DNA, Complementary - analysis; DNA-Binding Proteins - deficiency; DNA-Binding Proteins - genetics; Gene Expression; Genes; Genetic research; Ku Autoantigen; Mutation; Nuclear Proteins - deficiency; Nuclear Proteins - genetics; Oligonucleotide Array Sequence Analysis; Protein binding; Protein kinases; Space life sciences; Transcription (Genetics); Tumor proteins; Non-programmatic
• ISSN: 0449-3060
• DOI: 10.1269/jrr.42.371

The ability of cells to rejoin DNA double-strand breaks (DSBs) usually correlates with their radiosensitivity. This correlation has been demonstrated in radiosensitive cells, including the Chinese hamster ovary mutant XRS-5. XRS-5 is defective in a DNA end-binding protein, Ku80, which is a component of a DNA-dependent protein kinase complex used for joining strand breaks. However, Ku80-deficient cells are known to be retarded in cell proliferation and growth as well as other yet to be identified defects. Using custom-made 600-gene cDNA microarray filters, we found differential gene expressions between the wild-type and XRS-5 cells. Defective Ku80 apparently affects the expression of several repair genes, including topoisomerase-I and -IIA, ERCC5, MLH1, and ATM. In contrast, other DNA repair-associated genes, such as GADD45A, EGR1 MDM2 and p53, were not affected. In addition, for large numbers of growth-associated genes, such as cyclins and clks, the growth factors and cytokines were also affected. Down-regulated expression was also found in several categories of seemingly unrelated genes, including apoptosis, angiogenesis, kinase and signaling, phosphatase, stress protein, proto-oncogenes and tumor suppressors, transcription and translation factors. A RT-PCR analysis confirmed that the XRS-5 cells used were defective in Ku80 expression. The diversified groups of genes being affected could mean that Ku80, a multi-functional DNA-binding protein, not only affects DNA repair, but is also involved in transcription regulation. Our data, taken together, indicate that there are specific genes being modulated in Ku80- deficient cells, and that some of the DNA repair pathways and other biological functions are apparently linked, suggesting that a defect in one gene could have global effects on many other processes.