Identification of thyroid hormone-responsive genes in a chicken hepatoma cell line, LMH

Thyroid hormone receptors (TRs) are ligand-dependent transcription factors that regulate the transcription of multiple thyroid hormone (TH)-responsive genes. Our study aimed to identify TH-responsive genes in an estrogen-responsive chicken hepatoma cell line, LMH. RNA was prepared from cells treated with or without 10(-8) M 3,3',5-triiodothyronine (T3) for 24 h and was analyzed by differential display. At least six cDNAs were detected whose transcript increased in the presence of T3, and four of them were cloned. The four candidate TH-responsive genes that were identified had high similarity (>83%) to known chicken or mammalian genes, which included the ribosomal protein L7 gene; the cytoplasmic dynein heavy chain gene; the scaffold attachment factor A (SAF-A) gene, also known as heterogeneous nuclear ribonucleoprotein U (hnRNP U); and a gene for an unknown protein. Real-time PCR confirmed that the transcription of the four genes was responsive to T3; their transcript levels increased from four to eleven times with the administration of T3. The amount of TRbeta transcript did not change with the administration of T3. The physiological reasons for the activation of these genes and the utility of this cell line are discussed.