title: The gene regulating activity of thyroid hormone nuclear receptors is modulated by cell-type specific factors.
abstract: To understand whether the transcriptional activity of thyroid hormone nuclear receptors (TRs) is modulated by cell-type specific factors, full length TR subtype alpha1 (TRalpha1) and beta1 (TRbeta1) cDNAs were cloned from human hepatoma cell lines: HA22T, SK-Hep-1 and HepG2. The cloned receptor bound to the thyroid hormone 3,3',5-triiodo-L-thyronine (T3) and the thyroid hormone response elements (TREs) similarly to those cloned from other tissues. They exhibited T3- and TRE-dependent transactivation activities, indicating these TRs were transcriptionally active. The lipogenic malic enzyme (ME), a T3-target gene in liver, was stimulated approximately 3- and 1.5-fold by T3 in HA22T and SK-Hep-1, respectively. The T3-stimulated ME gene expression was inhibited in HA22T, but stimulated in SK-Hep-1 cells by insulin. These results suggest that the gene regulating activity of TRs was modulated by cell-type specific factors. Furthermore, these cell-type specific factors could modulate the cross talk between TR- and insulin receptor-mediated pathways.
authors.affiliation: Graduate Institute of Clinical Medicine, Chang-Gung College of Medicine and Technology, Taoyuan, Taiwan.
authors.forename: K
authors.initials: K
authors.lastname: Lin
authors.forename: S l
authors.initials: Sl
authors.lastname: Chen
authors.forename: X G
authors.initials: XG
authors.lastname: Zhu
authors.forename: H
authors.initials: H
authors.lastname: Shieh
authors.forename: P
authors.initials: P
authors.lastname: McPhie
authors.forename: S
authors.initials: S
authors.lastname: Cheng
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D011988:Receptors, Thyroid Hormone / Q000235:genetics* / Q000378:metabolism; D013963:Thyroid Hormones / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
chemical_list: D009687:Nuclear Proteins; D011988:Receptors, Thyroid Hormone; D013963:Thyroid Hormones