Region-specific chromatin decondensation and micronucleus formation induced by 5-azacytidine in human TIG-7 cellsSatoh T. · Yamamoto K. · Miura K.F. · Sofuni T.
aGenome Medical Business Division, Olympus Corporation, Hachioji; bDepartment of Cell Biology, Tokyo Metropolitan Institute of Gerontology, Itabashi; cNovusGene Inc., Hachioji (Japan)
A human diploid lung fibroblast cell strain, TIG-7, has a heteromorphic chromosome 15 with an extra short arm carrying a homogeneously staining region (15p+hsr). We demonstrated previously that the 15p+hsr consists of an inactive and G+C-rich rDNA cluster characterized by fluorescence in situ hybridization (FISH) and various chromosome banding techniques. Thus, it was suggested that the region could contain highly methylated DNA. To observe methylation status on the target region directly under the microscope, we used a demethylating agent, 5-azacytidine (5-azaC), to induce decondensation of the chromatin containing methylated DNA. At 24 h after treatment with 0.5 µM 5-azaC, marked decondensation of the 15p+hsr was observed in almost all of the metaphases. Furthermore, we observed micronuclei, which were equivalent to the rDNA of the 15p+hsr demonstrated by FISH in the same preparation. In contrast, the DNA cross-linking agent mitomycin C (MMC) preferentially induced 15p+hsr-negative micronuclei. These findings indicated that chromatin decondensation and subsequent DNA strand breakage induced by the demethylating effect of 5-azaC led specifically to 15p+hsr-positive micronuclei.
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Received 15 September 2003;
accepted 16 December 2003.
Number of Print Pages : 6
Number of Figures : 4, Number of Tables : 2, Number of References : 28
Cytogenetic and Genome Research
Formerly ‘Cytogenetics and Cell Genetics’
Vol. 104, No. 1-4, Year 2004 (Cover Date: 2004)
Journal Editor: H.P. Klinger, Bronx, N.Y.; M. Schmid, Würzburg
ISSN: 1424–8581 (print), 1424–859X (Online)
For additional information: http://www.karger.com/journals/cgr