NF-Y mediates the transcriptional inhibition of the cyclin B1, cyclin B2, and cdc25C promoters upon induced G2 arrest

During normal cell cycles, the function of mitotic cyclin-cdk1 complexes, as web as of cdc25C phosphatase, is required for G(2) phase progression. Accordingly, the G(2) arrest induced by DNA damage is associated with a down-regulation of mitotic cyclins, cdk1, and cdc25C phosphatase expression. We found that the promoter activity of these genes is repressed in the G(2) arrest induced by DNA damage. We asked whether the CCAAT-binding NF-Y modulates mitotic cyclins, cdk1, and cdc25C gene transcription during this type of G(2) arrest. In our experimental conditions, the integrity of the CCAAT boxes of cyclin B1, cyclin B2, and cdc25C promoters, as well as the presence of a functional NF-Y complex, is strictly required for the transcriptional inhibition of these promoters. Furthermore, a dominant-negative p53 protein, impairing doxorubicin-induced G(2) arrest, prevents transcriptional down-regulation of the mitotic cyclins, cdkl, and cdc25C genes. We conclude that, as already demonstrated for cdk1, NF-Y mediates the transcriptional inhibition of the mitotic cyclins and the cdc25C genes during p53-dependent G(2) arrest induced by DNA damage. These data suggest a transcriptional regulatory role of NF-Y in the G(2) checkpoint after DNA damage.