Transcriptional activation of tobacco E2F is repressed by co-transfection with the retinoblastoma-related protein: cyclin D expression overcomes this repressor activity
Transcriptional activation of tobacco E2F is repressed by co-transfection with the retinoblastoma-related protein: cyclin D expression overcomes this repressor activity
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DOI：
10.1007/s11103-004-6601-x
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发表时间：
2004
影响因子：
5.1
通讯作者：
Kenji Uemukai;H. Iwakawa;S. Kosugi;Sarah de Uemukai;K. Kato;E. Kondorosi;J. Murray;Masaki Ito;A. Shinmyō;M. Sekine
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文献类型：
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作者：
Kenji Uemukai;H. Iwakawa;S. Kosugi;Sarah de Uemukai;K. Kato;E. Kondorosi;J. Murray;Masaki Ito;A. Shinmyō;M. Sekine
越来越多的证据表明，转录因子E2F家族在植物G1/S转变过程中对基因表达的调控起着重要作用。在G1/S期特异性表达的烟草增殖细胞核抗原（PCNA）中，两个E2F结合位点协同作用于同步烟草BY-2细胞G1/S期的转录激活，启动子构建体与报告基因融合。此外，我们已经分离出烟草dpcdna (NtDP)，并表明在瞬时表达试验中，通过同时转染表达NtE2F和NtDP的质粒，可以观察到报告基因的显著激活。与表达NtRBR1的质粒共转染可抑制这种转录激活；体外下拉实验还显示，NtRBR1直接与NtE2F结合，从而潜在地阻断NtE2F的转录激活。重要的是，当NtRBR1与表达细胞周期蛋白D但不与细胞周期蛋白a或细胞周期蛋白b的质粒进一步共转染时，这种抑制活性被取消。这些结果与NtRBR1对NtE2F/NtDP复合物的抑制活性有关。
Evidence is emerging that the E2F family of transcription factors plays an important role in the regulation of gene expression at the G1/S transition in plants. Here, we show that in the tobacco proliferating cell nuclear antigen (PCNA), whose transcript is specifically expressed at G1/S phase, the two E2F binding sites are synergistically responsible for transcriptional activation at G1/S phase in synchronized tobacco BY-2 cells transformed with promoter constructs fused to a reporter gene. In addition, we have isolated the tobaccoDPcDNA (NtDP) and showed that significant activation of the reporter gene was observed in transient expression assays by concomitantly transfecting with plasmids expressing NtE2F and NtDP. This transcriptional activation was repressed by co-transfection with a plasmid expressing NtRBR1;in vitropull-down assays also revealed that NtRBR1 binds directly to NtE2F, thereby potentially blocking the transcriptional activation of NtE2F. Importantly, this repressor activity was cancelled when NtRBR1 was further co-transfected with a plasmid expressing cyclin D but not with cyclin A or cyclin B. These results are discussed with respect to the repression activity of NtRBR1 on the NtE2F/NtDP complex.