Rapid inhibition of c-myc gene expression by a glucocorticoid in the avian oviduct.
The glucocorticoid dexamethasone (DEX) causes a rapid, reversible reduction in c-myc mRNA level in the oviducts of estrogen-treated, immature chickens. The c-myc mRNA level begins to decrease by 5 min after injection of 0.5 mg DEX, reaches a minimum of 10% of the control value by 30 min, and returns to 30-40% of the control value by 4 h post injection. This rapid effect of DEX on the c-myc mRNA level occurs in both diethylstilbestrol-stimulated and diethylstilbestrol-withdrawn oviducts. The effect is dose dependent, with reduction of the c-myc mRNA measured with as little as 10 micrograms DEX injection (0.03 micrograms/g BW). The effect of the steroid is gene specific with H2B histone mRNA displaying a significantly reduced response. The effect is also tissue specific with liver displaying an increase of 170% of control values in c-myc mRNA level by 30 min after injection of 0.5 mg DEX. The reduction of avian oviduct c-myc mRNA levels by DEX may play a role in glucocorticoid inhibition of cell proliferation in this tissue. The rapidity of the steroid effects on c-myc expression makes it likely that the steroid-induced reduction of c-myc mRNA levels represents a direct primary action of the steroid-receptor complex on the c-myc gene expression.
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Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905.
Lau
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Fink
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Spelsberg
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D000818:Animals; D002645:Chickens; D003907:Dexamethasone / Q000494:pharmacology*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D009857:Oncogenes / Q000187:drug effects*; D010057:Oviducts / Q000032:analysis / Q000187:drug effects*; D012333:RNA, Messenger / Q000187:drug effects*
D012333:RNA, Messenger; D003907:Dexamethasone