We have studied the regulation of the human c-myc proto-oncogene by glucocorticoid hormones in T lymbhoblastic leukemic cells. A significant decrease (50%) of the steady state levels of c-myc mRNA was observed as early as 3 h after dexamethasone treatment of CEM-1.3 human lymphoma cells, reaching less than 5% values, with respect to untreated cells, 24 h after hormone administration. Nuclear run-on experiments showed no modifications of the transcriptional rate from the first exon. However, a slight decrease (15%) of the transcript elongation from the first exon/first intron boundary was observed in the dexamethasone-treated cells. Using actinomycin D to block gene transcription, we have observed a significant increase in the rate of c-myc RNA specific decay after dexamethasone treatment. Furthermore, cycloheximide was able to overcome completely the dexamethasone-induced down-regulation of the c-myc gene expression. Our data suggest that dexamethasone is able to inhibit human c-myc gene expression primarily at the post-transcriptional level, through the synthesis of hormone-induced regulatory protein(s) controlling c-myc transcript stability.
|Number of pages||5|
|Journal||Nucleic Acids Research|
|Publication status||Published - Mar 11 1990|
ASJC Scopus subject areas
- Statistics, Probability and Uncertainty
- Applied Mathematics
- Health, Toxicology and Mutagenesis