Activation of CTP:phosphocholine cytidylyltransferase alpha expression during the S phase of the cell cycle is mediated by the transcription factor Sp1.
An essential step during cell division is induction of phosphatidylcholine biosynthesis. In this pathway, CTP:phosphocholine cytidylyltransferase alpha (CT alpha) plays an important regulatory role. Previous studies (Golfman, L. S., Bakovic, M., and Vance, D. E. (2001) J. Biol. Chem. 276, 43688-43692) demonstrated that CT alpha mRNA accumulates during S phase in preparation for cellular mitosis. We now demonstrate that increased binding of the transcription factor Sp1 to the proximal promoter of CT alpha is responsible for increased transcription during the S phase. The Sp1 binding element present in position -67/-62 is essential for activation, and the Sp1 site in position -31/-9 is required to enhance transcription. Inhibition of Sp1 expression by RNA interference abolished the enhanced expression of CT alpha. Immunoprecipitation studies demonstrated that Sp1 interacts with cyclin E, cyclin A, and cyclin-dependent kinase 2 during the S phase. We conclude that Sp1 binding to the CT alpha proximal promoter is necessary to enhance transcription during the S phase. This is the first elucidation of a mechanism by which expression of a key enzyme in phospholipid biosynthesis is regulated during the cell cycle.
Banchio
Claudia
C
Department of Biochemistry and Canadian Institutes of Health Research Group on Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta, T6G 2S2, Canada.
Schang
Luis M
LM
Vance
Dennis E
DE
D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D019916:Choline-Phosphate Cytidylyltransferase / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D051379:Mice; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D016196:S Phase; D016329:Sp1 Transcription Factor / Q000378:metabolism / Q000502:physiology*
D016329:Sp1 Transcription Factor; D019916:Choline-Phosphate Cytidylyltransferase