Mouse sterol response element binding protein-1c gene expression is negatively regulated by thyroid hormone.
Sterol regulatory element-binding protein (SREBP)-1c is a key regulator of fatty acid metabolism and plays a pivotal role in the transcriptional regulation of different lipogenic genes mediating lipid synthesis. In previous studies, the regulation of SREBP-1c mRNA levels by thyroid hormone has remained controversial. In this study, we examined whether T3 regulates the mouse SREBP-1c mRNA expression. We found that T3 negatively regulates the mouse SREBP-1c gene expression in the liver, as shown by ribonuclease protection assays and real-time quantitative RT-PCR. Promoter analysis with luciferase assays using HepG2 and Hepa1-6 cells revealed that T3 negatively regulates the mouse SREBP-1c gene promoter (-574 to +42) and that Site2 (GCCTGACAGGTGAAATCGGC) located around the transcriptional start site is responsible for the negative regulation by T3. Gel shift assays showed that retinoid X receptor-alpha/thyroid hormone receptor-beta heterodimer bound to Site2, but retinoid X receptor-alpha/liver X receptor- heterodimer could not bind to the site. In vivo chromatin immunoprecipitation assays demonstrated that T3 induced thyroid hormone receptor-beta recruitment to Site2. Thus, we demonstrated that mouse SREBP-1c mRNA is down-regulated by T3 in vivo and that T3 negatively regulates mouse SREBP-1c gene transcription via a novel negative thyroid hormone response element: Site2.
Hashimoto
Koshi
K
Department of Medicine and Molecular Science, Graduate School of Medicine, Gunma University, 3-39-15 Showa-machi Maebashi, Gunma 371-8511, Japan. khashi@med.gunma-u.ac.jp
Yamada
Masanobu
M
Matsumoto
Shunichi
S
Monden
Tsuyoshi
T
Satoh
Teturou
T
Mori
Masatomo
M
D000818:Animals; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular; D002460:Cell Line; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D015536:Down-Regulation / Q000187:drug effects; D017353:Gene Deletion; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007668:Kidney; D008099:Liver / Q000737:chemistry; D008113:Liver Neoplasms; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D011988:Receptors, Thyroid Hormone / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D047488:Retinoid X Receptors / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051780:Sterol Regulatory Element Binding Protein 1 / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014284:Triiodothyronine / Q000494:pharmacology*
D012333:RNA, Messenger; D011988:Receptors, Thyroid Hormone; D047488:Retinoid X Receptors; C497388:Srebf1 protein, mouse; D051780:Sterol Regulatory Element Binding Protein 1; D014284:Triiodothyronine