Activation of the hprt gene on the inactive X chromosome in transformed diploid female Chinese hamster cells.
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Journal of cell science
Publication Date / Copyright Date
Company of Biologists
Treatment with 5-azacytidine, a potent inhibitor of DNA methylation, was used to induce activation of the selectable hprt gene on the inactive X chromosome in a diploid female Chinese hamster cell line. The transformed, stably diploid cell line F3B was selected in media containing the lethal purine analogue 6-thioguanine, to generate a phenotypically HPRT- mutant, F3BT1, of presumed genotype hprt-/hprt(+), where (+) represents the presumably wild-type allele on the inactive X chromosome. Treatment of F3BT1 with 5-azacytidine resulted in phenotypic reversion to HPRT+ at a frequency greater than 10(-3). Similar treatment of 6-thioguanine-resistant control lines derived from male cells, or from CHO (which has no inactive X chromosome), had no effect on the frequency of phenotypic reversion, indicating that activation of the hprt(+) allele, rather than reversion of the hprt- is responsible. This conclusion is substantiated by documentation of the low mutagenic capacity of 5-azacytidine in this system. Proof that the hprt(+) allele can be activated by 5-azacytidine treatment was obtained in somatic cell hybrids in which hprt gene products from the active and inactive X chromosomes could be distinguished by isoelectric focusing. Our results demonstrate that X-linked gene activation associated with generalized DNA demethylation occurs with high frequency in transformed diploid Chinese hamster cells.
Medical Specialties | Medicine and Health Sciences | Osteopathic Medicine and Osteopathy
Animals, Azacitidine, Cell Line, Transformed, Cricetinae, Diploidy, Enzyme Induction, Female, Gene Expression Regulation, Enzymologic, Genotype, Hypoxanthine Phosphoribosyltransferase, Isoelectric Focusing, Mutation, Phenotype, Transcriptional Activation, X Chromosome
Grant, S G. and Worton, R G., "Activation of the hprt gene on the inactive X chromosome in transformed diploid female Chinese hamster cells." (1989). Faculty Articles. 1532.