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Updated: Aug 13, 2026

Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations
Published on: September 17, 2012
Modulation of Sp1 activity by a cyclin A/CDK complex
E Haidweger1, M Novy, H Rotheneder
1Institute of Medical Biochemistry, Division of Molecular Biology, Vienna Biocenter, University of Vienna, Vienna, A-1030, Austria.
Abstract:
Transcription factors of the Sp1 family are targets of several regulatory pathways and can induce or inhibit gene expression. Here we show that Sp1 is associated with a histone 1 kinase activity. This activity is growth regulated and correlates with the expression of cyclin A. Co-immunoprecipitation experiments demonstrate, that Sp1 interacts with cyclin A and can be phosphorylated by a cyclin A associated kinase. The interaction is direct and requires the zinc-finger region of Sp1 and the amino-terminal domain of cyclin A. Over-expression of cyclin A enhances the expression of a reporter gene controlled by an Sp1 responsive promoter. Addition of olomoucine, a specific inhibitor of CDK2 and CDC2 activity on the other hand reduces the expression of the reporter. Electrophoretic mobility shift assays suggest that this is due to a reduction of the DNA-binding ability of Sp1 family members. Our results indicate that phosphorylation of Sp1 and other members of the family by a cyclin A/CDK complex may play a role in the growth and cell cycle regulation of its transcriptional activity.
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