Phosphorylation of Sp1 by Cyclin-dependent Kinase 2 Modulates the Role of Sp1 in CTP:Phosphocholine Cytidylyltransferase α Regulation during the S Phase of the Cell Cycle

• Published in: The Journal of biological chemistry 2004-09, Vol.279 (38), p.40220-40226
• Main Authors: Banchio, Claudia, Schang, Luis M., Vance, Dennis E.
• Format: Article
• Language: English
• Subjects: Animals; Blood Proteins - pharmacology; CDC2-CDC28 Kinases - antagonists & inhibitors; CDC2-CDC28 Kinases - genetics; CDC2-CDC28 Kinases - metabolism; Cells, Cultured; Choline-Phosphate Cytidylyltransferase - genetics; Choline-Phosphate Cytidylyltransferase - metabolism; Cyclin A - genetics; Cyclin A - metabolism; Cyclin E - genetics; Cyclin E - metabolism; Cyclin-Dependent Kinase 2; Enzyme Inhibitors - pharmacology; Fibroblasts - cytology; Gene Expression Regulation, Enzymologic; Genes, Reporter; Mice; Mice, Inbred C3H; Phosphorylation; RNA, Small Interfering; S Phase - physiology; Sp1 Transcription Factor - metabolism; Transcription, Genetic
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M406468200

Phosphatidylcholine is the major lipid component in mammalian membranes. Phosphatidylcholine synthesis increases in C3H10T1/2 fibroblasts during the G1 and S phases of the cell cycle. Previous studies demonstrated that the mRNA encoding CTP:phosphocholine cytidylyltransferase α (CTα) increases during S phase (Golfman, L. S., Bakovic, M., and Vance, D. E. (2001) J. Biol. Chem. 276, 43688-43692) and that this activation is driven by increased binding of Sp1 to the CTα promoter (Banchio, C., Schang, L. M., and Vance, D. E. (2003) J. Biol. Chem. 278, 32457-32464). We now demonstrate that cyclin-dependent kinase 2 (CDK2) phosphorylation of Sp1 activates CTα transcription during S phase. Sp1 binds in a phosphorylated state to the CTα promoter. Sp1 binding is enhanced by association with cyclin A/E and CDK2, both in vivo and in vitro. In cells that overexpress Sp1, co-expression of cyclin A and CDK2 induces a high and constant level of CTα expression, whereas reduction in the expression of cyclin A, cyclin E, and CDK2 eliminates the induction of CTα expression in S phase. Furthermore, CTα expression is decreased in cells overexpressing a dominant-negative form of CDK2 and in cells treated with the CDK2 kinase inhibitors roscovitine and olomoucine. These results enhance our understanding of the regulatory mechanisms involved in the expression of CTα in preparation for cell division.