Inhibition of retinoic acid-inducible transcription by COUP-TFI in human salivary gland adenocarcinoma cell line HSG.
Human salivary gland adenocarcinoma cells (HSG) express nuclear receptors, all-trans-retinoic acid (at-RA) receptors (RARs), and retinoid X/9-cis-retinoic acid (9-c-RA) receptors (RXRs). In order to investigate whether the endogenous RARs or RXRs of HSG cells can induce transcription activation, the thymidine kinase promoter (TK)-driven luciferase reporter gene containing the retinoic acid response element (RARE), of RARbeta, betaRARE2-TK-Luc, was transfected into HSG cells and ligand-dependent transcription activation was examined. Luciferase activity of cell lysate increased by the treatment with either at-RA or 9-c-RA. Co-transfection of RARalpha and (or) RXRalpha-expression plasmids with the reporter gene enhanced the luciferase activity, suggesting that endogenous RARs and RXRs work as ligand-dependent transfactors in HSG cells. Reverse transcriptase - polymerase chain reaction analysis revealed that HSG cells express chicken ovalbumin upstream promoter - transcription factor I (COUP-TFI). Co-transfection of COUP-TFI-expression plasmid suppressed the at-RA-induced transcription activation of the reporter gene. Similar results were shown using a chromatin-integrated reporter gene system, using a stably transfected beta-RARE2-TK-beta-galactosidase (beta-Gal) reporter gene. The at-RA-dependent increase in the beta-Gal expression was completely inhibited by COUP-TFI. The transfection of antisense oligonucleotide of COUP-TFI squelched the RA-dependent growth inhibition induced by RAR-RXR heterodimers. Conclusively, RARs and RXRs of HSG cells are functional and play roles as transactivators in at-RA-sensitive processes such as the proliferation or differentiation of cells. COUP-TFI very likely regulates these processes by repressing the functions of these transactivators.
Kyakumoto
S
S
Department of Biochemistry, Iwate Medical University, School of Dentistry, Morioka, Japan. kyakumot@iwate-med.ac.jp
Ota
M
M
Sato
N
N
D000230:Adenocarcinoma / Q000378:metabolism*; D000818:Animals; D051838:COUP Transcription Factor I; D002455:Cell Division; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D016372:RNA, Antisense / Q000378:metabolism; D051381:Rats; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D020218:Response Elements; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012468:Salivary Gland Neoplasms / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology*; D014212:Tretinoin / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D051838:COUP Transcription Factor I; D004268:DNA-Binding Proteins; D008024:Ligands; C497589:NR2F1 protein, human; C497591:Nr2f1 protein, rat; D016372:RNA, Antisense; D018168:Receptors, Retinoic Acid; D014157:Transcription Factors; D014212:Tretinoin