Manni I, Mazzaro G, Gurtner A, Mantovani R, Haugwitz U, Krause K, Engeland K, Sacchi A, Soddu S, Piaggio G
Laboratorio Oncogenesi Molecolare, Istituto Regina Elena, Rome 00158, Italy.
J Biol Chem. 2001 Feb 23;276(8):5570-6. doi: 10.1074/jbc.M006052200. Epub 2000 Nov 28.
During normal cell cycles, the function of mitotic cyclin-cdk1 complexes, as well as of cdc25C phosphatase, is required for G2 phase progression. Accordingly, the G2 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 G2 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 G2 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 G2 arrest, prevents transcriptional down-regulation of the mitotic cyclins, cdk1, 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 G2 arrest induced by DNA damage. These data suggest a transcriptional regulatory role of NF-Y in the G2 checkpoint after DNA damage.
在正常细胞周期中，有丝分裂周期蛋白 - cdk1复合物以及cdc25C磷酸酶的功能是G2期进程所必需的。因此，DNA损伤诱导的G2期阻滞与有丝分裂周期蛋白、cdk1和cdc25C磷酸酶表达的下调相关。我们发现这些基因的启动子活性在DNA损伤诱导的G2期阻滞中受到抑制。我们询问CCAAT结合蛋白NF - Y是否在这种类型的G2期阻滞过程中调节有丝分裂周期蛋白、cdk1和cdc25C基因的转录。在我们的实验条件下，细胞周期蛋白B1、细胞周期蛋白B2和cdc25C启动子的CCAAT框的完整性以及功能性NF - Y复合物的存在，对于这些启动子的转录抑制是严格必需的。此外，一种显性负性p53蛋白，它会损害阿霉素诱导的G2期阻滞，可防止有丝分裂周期蛋白、cdk1和cdc25C基因的转录下调。我们得出结论，正如已经在cdk1中证明的那样，NF - Y在DNA损伤诱导的p53依赖性G2期阻滞过程中介导有丝分裂周期蛋白和cdc25C基因的转录抑制。这些数据表明NF - Y在DNA损伤后的G2检查点中具有转录调节作用。
