Dephosphorylation of Sp1 by Protein Phosphatase 1 Is Involved in the Glucose-mediated Activation of the Acetyl-CoA Carboxylase Gene

• Published in: The Journal of biological chemistry Vol. 271; no. 25; pp. 14692 - 14697
• Main Authors: Daniel, S, Zhang, S, DePaoli-Roach, A A, Kim, K H
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 21-06-1996
• Subjects: Acetyl-CoA Carboxylase - biosynthesis; Acetyl-CoA Carboxylase - genetics; Adipocytes; Animals; Base Sequence; Binding Sites; Cell Line; Cell Nucleus - metabolism; Chloramphenicol O-Acetyltransferase - biosynthesis; DNA - chemistry; DNA - metabolism; Enzyme Inhibitors - pharmacology; Ethers, Cyclic - pharmacology; Gene Expression Regulation, Enzymologic - drug effects; Glucose - pharmacology; Mice; Molecular Sequence Data; Okadaic Acid; Oligodeoxyribonucleotides; Phosphoprotein Phosphatases - metabolism; Phosphoproteins - metabolism; Promoter Regions, Genetic; Protein Denaturation; Protein Folding; Protein Phosphatase 1; Recombinant Fusion Proteins - biosynthesis; Sp1 Transcription Factor - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.271.25.14692

When mouse 30A5 preadipocytes are exposed to high glucose concentrations, acetyl-CoA carboxylase is induced through glucose
activation of promoter II of the acetyl-CoA carboxylase gene. Glucose treatment of the cells increases Sp1 binding to two
GC-rich glucose response elements in promoter II. We have investigated the mechanism by which glucose increases Sp1 binding
and transactivation of promoter II in 30A5 cells. DNA mobility shift assays have shown that nuclear extracts from glucose-treated
cells exhibit increased Sp1 binding activity. This increase in the binding activity is not due to glucose-mediated changes
in the amount of Sp1 in the nucleus but to an increase in the activity that modifies Sp1 so that it binds more effectively
to the promoter sequence. This Sp1 modifying activity is inhibited by okadaic acid and phosphatase inhibitor 2, and has a
molecular mass of 38–42 kDa. The catalytic subunit of type 1 protein phosphatase, whose molecular mass is 38 kDa, also increased
the ability of Sp1 to bind to promoter II. Treatment of nuclear extract with antibodies against the catalytic subunit partially
suppressed the nuclear activity for Sp1 activation. From these results, we conclude that the Sp1 transcription factor exhibits
enhanced binding to promoter II and transcriptional activation is the result of glucose-induced dephosphorylation by type
1 phosphatase.