Phosphorylation of the CCAAT displacement protein (CDP)/Cux transcription factor by cyclin A-Cdk1 modulates its DNA binding activity in G(2).
Stable DNA binding by the mammalian CCAAT displacement protein (CDP)/Cux transcription factor was previously found to be up-regulated at the G(1)/S transition as the result of two events, dephosphorylation by the Cdc25A phosphatase and proteolytic processing, to generate an amino-truncated isoform of 110 kDa. In S phase, CDP/Cux was shown to interact with and repress the core promoter of the p21(WAF1) gene. Here we demonstrate that DNA binding by p110 CDP/Cux is down-modulated as cells progress into G(2). Accordingly, cyclin A-Cdk1 was found to bind to CDP/Cux and modulate its DNA binding activity in vitro and in vivo. Interaction with CDP/Cux required the presence of both cyclin A and a cyclin-dependent kinase (Cdk)-activating kinase-activated Cdk1 and involved the Cut homeodomain and a downstream Cy motif. Phosphorylation of serines 1237 and 1270 caused inhibition of DNA binding in vitro. In cotransfection studies, cyclin A-Cdk1 inhibited CDP/Cux stable DNA binding and prevented repression of the p21(WAF1) reporter. In contrast, mutant CDP/Cux proteins in which serines 1237 and 1270 were replaced with alanines were not affected by cyclin A-Cdk1. In summary, our results suggest that the phosphorylation of CDP/Cux by cyclin A-Cdk1 contributes to down-modulate CDP/Cux activity as cells progress into the G(2) phase of the cell cycle.
Santaguida
M
M
Molecular Oncology Group, McGill University Health Center, Department of Biochemistry, McGill University Hamilton, Ontario L8N 3Z5, Canada.
Ding
Q
Q
Bérubé
G
G
Truscott
M
M
Whyte
P
P
Nepveu
A
A
D000818:Animals; D001483:Base Sequence; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D002460:Cell Line; D019925:Cyclin A / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D017931:DNA Primers; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors
C080632:CUX1 protein, human; C000624101:Cux1 protein, mouse; D019925:Cyclin A; D017931:DNA Primers; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D004247:DNA; D016203:CDC2 Protein Kinase