Differential gene expression in a DNA double-strand-break repair mutant XRS-5 defective in Ku80: analysis by cDNA microarray.
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.
Chan
J Y
JY
Institute of Radiological Sciences, National Yang Ming University, Taipei, Taiwan.
Chen
L K
LK
Chang
J F
JF
Ting
H M
HM
Goy
C
C
Chen
J L
JL
Hwang
J J
JJ
Chen
F D
FD
Chen
D J
DJ
Ngo
F Q
FQ
D000818:Animals; D034961:Antigens, Nuclear; D016466:CHO Cells; D006224:Cricetinae; D004265:DNA Helicases; D004260:DNA Repair / Q000235:genetics*; D018076:DNA, Complementary / Q000032:analysis; D004268:DNA-Binding Proteins / Q000172:deficiency* / Q000235:genetics*; D015870:Gene Expression; D000072200:Ku Autoantigen; D009154:Mutation; D009687:Nuclear Proteins / Q000172:deficiency* / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis
D034961:Antigens, Nuclear; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen