Isolation and characterization of the E2F‐like gene in plants

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Abstract
The transcription factor E2F regulates the expression of genes involved in the progression of G1/S transition and DNA replication in mammalian cells. We cloned and characterized a cDNA (NtE2F) corresponding to a E2F homolog of tobacco (Nicotiana tabacum). The transcription of NtE2F was induced as cells progressed from G1 to the S phase and expressed much earlier than that of the proliferating cell nuclear antigen (PCNA) gene. We demonstrated that NtE2F can interact with the tobacco retinoblastoma (Rb)‐related protein in a yeast two‐hybrid assay. To further characterize NtE2F, the trans‐activation activity of NtE2F was examined by using a transient assay in the tobacco Bright Yellow‐2 (BY‐2) cells with NtE2F fused to the DNA‐binding domain of the yeast transcriptional activator GAL4. NtE2F activated the transcription of the β‐glucuronidase (GUS) reporter gene driven by a cauliflower mosaic virus (CaMV) 35S core promoter containing the GAL4‐binding sequence. This is the first report of the identification of a functionally equivalent E2F‐like gene in plants.