Abstract
E2F transcription factors regulate the expression of genes required for the G1/S transition of cell cycle (e.g. DNA replication), and E2F family is negatively controlled by Rb (retinoblastoma) family proteins in mammalin cells. We have previously demonstrated that the tobacco NtE2F exhibits transactivation activity using a transient assay in tobacco BY-2 cells. To further analyze the regulation of transcriptional activity of NtE2F, we construct the experimental system using the PCNA gene expressed predominantly in late G1 to S phase. It is indicated that transcriptional activity of NtE2F is repressed by tobacco Rb (NtRb). In addition, the inhibitory activity of NtRb was blocked when it was further co-transfected with plasmid encoding cyclin D but not cyclin A or cyclin B.
Our results suggest that NtRb is a potent repressor of NtE2F activity and the control of the G1/S transition is likely mediated by E2F/Rb/cyclinD pathway in plant cells.
