Thyroid Hormone Regulation of Transcription Factors Involved in Malic Enzyme Gene Expression

• Published in: The Journal of biological chemistry Vol. 264; no. 19; pp. 11483 - 11490
• Main Authors: Petty, K J, Morioka, H, Mitsuhashi, T, Nikodem, V M
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 05.07.1989; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Base Sequence; Biological and medical sciences; Cell Nucleus - analysis; Cell physiology; Deoxyribonuclease I; DNA - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - drug effects; HeLa Cells; Hormonal regulation; Humans; Hyperthyroidism - metabolism; Hypothyroidism - metabolism; Kidney - ultrastructure; Kinetics; Liver - ultrastructure; Malate Dehydrogenase - genetics; Male; Molecular and cellular biology; Mutation; Nuclear Proteins - metabolism; Promoter Regions, Genetic; Rats; Rats, Inbred Strains; Regulatory Sequences, Nucleic Acid; Transcription Factors - metabolism; Transcription, Genetic - drug effects; Triiodothyronine - pharmacology; Ligand binding; Rat; Transcription; Gel electrophoresis; Rodentia; Malate dehydrogenase; Hela cell line; Vertebrata; Regulation(control); Mammalia; Deletion; Regulatory sequence; Triiodothyronine; Kinetics; Molecular cloning; Transcription factor; Mechanism of action
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)60489-2

The mechanisms by which triiodothyronine (T3) regulates gene transcription are inadequately understood. In order to examine the effect of T3 on transcriptional mechanisms, we utilized several techniques to characterize trans-acting factors which interact with cis-regulatory elements of the promoter for the T3-responsive rat malic enzyme gene. Transcription of deletion mutants of the promoter by HeLa extracts revealed the existence of three cis-regulatory elements at −144 to −123, −70 to −50, and −30 to +5 (relative to the cap site at +1). DNase I footprinting disclosed the presence of proteins which bound to each of these regions. Gel mobility shift assays showed that specific binding of liver nuclear proteins to two of these regions (−144/−114 and −76/−47) was diminished in hypothyroid and elevated in hyperthyroid rats. Similar but less marked effects of T3 on the binding of kidney (a T3-responsive tissue) nuclear proteins to the −76/−47 and cap site regions were observed while binding of testis (a T3-nonresponsive tissue) nuclear proteins was unaffected by T3 treatment. Changes in the magnitude and time course of binding of liver proteins to this promoter correlated closely with previously documented T3-induced increases in the hepatic malic enzyme gene transcription rate. These results are consistent with a model in which the regulation of malic enzyme gene transcription by T3 in responsive tissues is mediated in part by hormone-induced increases in the binding of trans-acting factors to cis-regulatory elements.