Estrogen stimulates transcription of c-jun protooncogene.
Estrogen is a mitogen for the rat uterus, where it induces transient activation of c-fos and c-myc protooncogene expression, followed by increases in DNA synthesis and cell proliferation. JUN-C, the product of the c-jun protooncogene, is a nuclear protein that can interact with FOS to modulate the activity of AP-1-responsive promoters. To test whether c-jun is a target for estrogen regulation, we measured the effects of 17 beta-estradiol on the expression of this gene in rat uterus. A human c-jun cDNA probe detects in rat uterus two mRNA species of 2.5 and 3.2 kilobases. Treatment of the animals with estrogen results in a rapid transient increase in the concentrations of these mRNAs; a 4- to 5-fold increase over the prestimulation level was detected starting 30 min after estrogen injection and lasting for 2 h, with a return to the prestimulation level after 4 h. In accordance with the results obtained by analysis of the mRNA, we found that estrogen increases 3- to 4-fold c-jun gene transcription in the uterus, at the same time it induces its mRNA accumulation. The ability of estrogen to induce c-jun gene expression was not abolished by the protein synthesis inhibitor cycloheximide, suggesting that transcriptional activation of this protooncogene is a primary response to the hormone. Furthermore, we found that in the estrogen-responsive MCF-7 human mammary carcinoma cells, estrogen stimulates transcription of a reporter gene containing four copies of a jun/AP-1 response element. These data demonstrate that c-jun gene expression is regulated by estrogen and suggest that JUN-C could play a role in the activation of cell proliferation by estrogen.
Weisz
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Istituto di Patologia Generale e Oncologia, Prima Facoltà di Medicina e Chirurgia, Università di Napoli, Italy.
Cicatiello
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Persico
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Scalona
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Bresciani
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F
D000818:Animals; D001483:Base Sequence; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D004351:Drug Resistance; D004742:Enhancer Elements, Genetic; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D016755:Proto-Oncogene Proteins c-jun; D011519:Proto-Oncogenes / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects; D014599:Uterus / Q000187:drug effects / Q000378:metabolism*
D004268:DNA-Binding Proteins; D004967:Estrogens; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D014157:Transcription Factors; D015500:Chloramphenicol O-Acetyltransferase