Increase in Ref-1 mRNA and protein by thyrotropin in rat thyroid FRTL-5 cells.
Thyrotropin (TSH) induces the expression of fos and jun family genes in thyroid cells. The DNA-binding activity of these gene products (AP-1) has been shown to be enhanced by ubiquitous nuclear redox factor-1 (Ref-1). We thus examined whether TSH regulates Ref-1 gene expression in rat thyroid FRTL-5 cells. Northern blot analysis revealed that the abundance of Ref-1 mRNA significantly increased within 3 hours after TSH followed by a sustained increase until 12 hours. The increase was also induced by treatment with forskolin but not in the presence of cycloheximide, indicating that the TSH effect on Ref-1 mRNA is mediated by intracellular cAMP and requires de novo protein synthesis. Consistent with the elevation of the mRNA level, Western blot analysis showed an increase in Ref-1 protein 3 hours after TSH. The level continued to increase until 12 hours. These results suggested that increased Ref-1 by TSH might regulate the binding activity of AP-1 in thyroid cells. Considering that Ref-1 also has a DNA repair function, Ref-1 may play dual roles in gene regulation and DNA repair processes in thyroid cells.
Asai
T
T
Department of Endocrinology and Metabolism, Research Institute of Environmental Medicine, Nagoya University, Japan.
Kambe
F
F
Kikumori
T
T
Seo
H
H
D000818:Animals; D015153:Blotting, Western; D019757:Carbon-Oxygen Lyases; D002460:Cell Line; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D009687:Nuclear Proteins / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D013961:Thyroid Gland / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology*
D009687:Nuclear Proteins; D012333:RNA, Messenger; D013972:Thyrotropin; D019757:Carbon-Oxygen Lyases; C470319:Apex1 protein, rat; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase