title: Down-regulation of bcl-xs gene expression in rat thymocytes by dexamethasone.
abstract: In order to test a hypothesis that the expression of bcl-x gene promotes apoptosis by antagonizing the function of bcl-2 gene product, time course of the expression of bcl-x was investigated using the dexamethasone-treated rat thymocytes which were undergoing apoptosis. Unexpectedly, dexamethasone suppressed the expression of bcl-x in a dose- and time-dependent manner. Such decrease was detected even in the presence of cycloheximide, suggesting that the suppression is due to the genomic (primary) effect of dexamethasone. Since the expression of bcl-xL, as measured by a specific nucleotide probe, was not detected at a quantifiable level, the decrease was apparently attributed to that in bcl-xS. Our present observations propose a new role of the bcl-xS gene product, in which the bcl-x gene product may be necessary for survival of immature thymocytes rather than for their apoptosis.
mesh_terms: D000818:Animals; D017209:Apoptosis; D001483:Base Sequence; D002478:Cells, Cultured; D003348:Cortisone / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D006854:Hydrocortisone / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis*; D019253:Proto-Oncogene Proteins c-bcl-2; D011519:Proto-Oncogenes / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013739:Testosterone / Q000494:pharmacology; D013950:Thymus Gland / Q000187:drug effects / Q000378:metabolism*; D051020:bcl-X Protein
chemical_list: C494813:Bcl2l1 protein, rat; D015345:Oligonucleotide Probes; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D013739:Testosterone; D004958:Estradiol; D003907:Dexamethasone; D003348:Cortisone; D006854:Hydrocortisone