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Transcriptional regulation of fatty acid synthase gene and ATP citrate‐lyase gene by Sp1 and Sp3 in rat hepatocytes 1
Author(s) -
Fukuda Hitomi,
Noguchi Tamio,
Iritani Nobuko
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)01700-7
Subject(s) - fatty acid synthase , microbiology and biotechnology , reporter gene , atp citrate lyase , gene expression , transfection , sp1 transcription factor , gene , transcription (linguistics) , endogeny , chemistry , acetyl coa carboxylase , fatty acid , enzyme , biology , promoter , biochemistry , pyruvate carboxylase , citrate synthase , linguistics , philosophy
When two copies of the sequences spanning −57 to −35 of the fatty acid synthase (FAS) or −64 to −41 of the ATP citrate‐lyase (ACL) gene linked to a reporter gene were transfected into primary cultured hepatocytes, the reporter activities significantly increased in response to insulin/glucose treatment. In cotransfection experiments of the FAS(−57/−35) with the Sp1 or Sp3 expression vector, the reporter activities of transcription were suppressed by Sp1 and stimulated by Sp3. In the cotransfection experiments of ACL(−64/−41), the activities were suppressed by Sp1 but were unchanged by Sp3. A similar effect of Sp1 and Sp3 on transcription was seen in mRNA concentrations and enzyme activities of endogenous FAS and ACL. Moreover, the mRNA concentrations and enzyme activities of endogenous acetyl‐CoA carboxylase were suppressed by Sp1 and greatly increased by Sp3. Gel mobility super shift assays using antibodies against Sp1 or Sp3 revealed the binding of the transcription factors Sp1 and Sp3 with the GC rich regions located within FAS(−57/−35) and ACL(−64/−41) genes. The formation of DNA‐protein complexes was decreased in rats fed a high‐carbohydrate diet in comparison with that in fasted rats, but feeding the corn oil diet inhibited this decrease. In Western immunoblotting assay, however, the amount of Sp1 and Sp3 remained unchanged in the dietary conditions. Therefore, the binding of DNA‐protein complexes was not due to changes in the amount of Sp1 and Sp3 but to changes in the binding activity, suggesting that these transcription factors may be an important determinant of lipogenic enzyme expression.