Reactivation of thyroglobulin gene expression in transformed thyroid cells by 5-azacytidine.
Transformed rat thyroid cells fail to express thyroglobulin. Cells transformed with a Kirsten murine sarcoma virus carrying a temperature-sensitive ras allele lose their transformation phenotype when shifted to the nonpermissive (39 degrees C) temperature. The thyroglobulin promoter, however, remains inactive. Similarly, transfection of these cells with a thyroglobulin promoter fused to a neomycin resistance reporter gene does not produce clones resistant to G418. Treatment of the transfected cells with the DNA demethylating agent 5-azacytidine reactivates the thyroglobulin promoter and yields stable G418-resistant clones. We show that thyroglobulin promoter activity is correlated with the presence of a thyroid-specific nuclear factor, TgTF1. TgTF1 cannot be detected in transformed cells but reappears after treatment with 5-azacytidine at 39 degrees C. Restoration of Ras activity at 33 degrees C leads to the rapid loss of TgTF1 and G418 resistance.
Avvedimento
E V
EV
Institute of Cancer Research, Columbia University, New York, New York 10032.
Obici
S
S
Sanchez
M
M
Gallo
A
A
Musti
A
A
Gottesman
M E
ME
D000818:Animals; D001374:Azacitidine / Q000494:pharmacology*; D001483:Base Sequence; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002471:Cell Transformation, Neoplastic; D003001:Cloning, Molecular; D005786:Gene Expression Regulation / Q000187:drug effects*; D005796:Genes / Q000187:drug effects*; D007708:Kirsten murine sarcoma virus / Q000235:genetics; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D011401:Promoter Regions, Genetic; D051381:Rats; D013954:Thyroglobulin / Q000235:genetics*; D013961:Thyroid Gland; D014158:Transcription, Genetic; D014162:Transfection
D015345:Oligonucleotide Probes; D013954:Thyroglobulin; D001374:Azacitidine