Minimum number of tobacco E2F - DP genes: 6
Count of tobacco E2F - DP sequences: 6
Pfam accession: E2F_TDP
SHOULD possess E2F_TDP domain
The E2F family of transcription factors plays an important role in cell cycle control by regulating the transcription of the genes involved in the progression to the S phase from the G1 (G0) phase of animal cells (for review, see Dyson, 1998 ; Lavia and Jansen-D¨¹rr, 1999). Yeast (Saccharomyces cerevisiae) lacks this protein family, whereas plants possess it. A recent finding has shown that tobacco (Nicotiana tabacum) ribonucleotide reducatse and proliferating cell nuclear antigen promoters contain E2F-binding sites, which function as cis-elements essential for the cell cycle-regulated expression of the gene (Chaboute et al., 2000 ; Egelkrout et al., 2001), suggesting that the E2F gene family is functional in the control of the plant cell cycle.
In animals, a number of the E2F family members have been identified; six E2F and two DP proteins for mammals, and two E2Fs and one DP for Drosophila melanogaster (Dynlacht et al., 1994; Dyson, 1998; Helin, 1998; Sawado et al., 1998). The E2F members form heterodimers with the DP members and activate transcription from genes responsible for cell cycle control, initiation of replication, and DNA synthesis, as well as several proto-oncogenes such as c-myb, B-myb, and c-myc in mammalian cells (Lavia and Jansen-D¨¹rr, 1999). On the other hand, pocket proteins (pRb, p107, and p130) interact with the E2F/DP complex to repress transcription of the E2F-regulated genes by masking the E2F transcriptional activation domain that overlaps with the Rb-binding region and/or recruitment of histone deacetylase activity to promoter sites that the E2F complex binds (Dyson, 1998; Lavia and Jansen-D¨¹rr, 1999).
In plants, a number of cDNAs encoding E2F or DP homologs have been isolated and characterized (Ram¨ªrez-Parra et al., 1999; Sekine et al., 1999; Albani et al., 2000; Magyar et al., 2000 ; Ram¨ªrez-Parra and Gutierrez, 2000). The plant E2Fs share high sequence similarity but have no distinguishable similarity with the animal E2F proteins although they slightly resemble E2F-4 and E2F-5. Like the E2F family from animals, the plant E2F proteins can bind to the consensus binding sites of the animal E2F (Albani et al., 2000) and their DNA-binding activities can be stimulated by the plant DP proteins and human DP-1 (Albani et al., 2000; Magyar et al., 2000; Ram¨ªrez-Parra and Gutierrez, 2000). It has been also shown that they can bind human Rb or Rb-like proteins from plants (Ram¨ªrez-Parra et al., 1999; Sekine et al., 1999). However, little is known about the properties of the plant E2Fs, including transactivation, subcellular localization, and functional differences (Kosugi S, Ohashi Y., 2001).
The various E2F proteins can recognize specific DNA cis-elements forming heterodimers with partially related proteins called DP. So far, six E2Fs and two DPs have been found in human cells, and, according to a comparative analysis of the genome of Arabidopsis thaliana, at least six putative E2F genes and two DP genes appear to be present in Arabidopsis cells as well. Plant E2F genes have been described in carrot, tobacco, and wheat, and three of the Arabidopsis E2Fs have been recently described, whereas DP homologues have been reported in wheat and Arabidopsis. All the E2F proteins described so far possess a highly conserved DNA-binding domain, forming a winged helix motif, which is flanked toward the C-terminal side by a DP dimerization domain containing a leucine heptad repeat. Next to the dimerization domain, all the E2Fs possess another conserved region called marked box, which in human cells is recognized by the adenovirus E4 protein and may be involved in heterodimerization and DNA bending (Mariconti L, et al., 2002).
Mariconti, L; Pellegrini, B; Cantoni, R; Stevens, R; Bergounioux, C; Cella, R; Albani, D. The E2F family of transcription factors from Arabidopsis thaliana. Novel and conserved components of the retinoblastoma/E2F pathway in plants. J. Biol. Chem. 2002. 277(12):9911-9 PMID: 11786543
de Jager, SM; Menges, M; Bauer, UM; Murra, JA. Arabidopsis E2F1 binds a sequence present in the promoter of S-phase-regulated gene AtCDC6 and is a member of a multigene family with differential activities. Plant Mol. Biol. 2001.47(4):555-68 PMID: 11669580
Zheng, N; Fraenkel, E; Pabo, CO; Pavletich, NP. Structural basis of DNA recognition by the heterodimeric cell cycle transcription factor E2F-DP. Genes Dev. 1999 13(6):666-74 PMID: 10090723
Kosugi S, Ohashi Y. Interaction of the Arabidopsis E2F and DP proteins confers their concomitant nuclear translocation and transactivation. Plant Cell. 2001 Oct;13(10):2269-81. PMID: 11891240
Number of contigs: 6
Number of singlets: 0
Total minimum number – 6
|E2F_2||[comment=Most likely AB025347.1]||
Paul J Rushton
Marta T. Bokowiec
Xianfeng (Jeff) Chen
Thomas (Tom) W Laudeman
Jennifer F. Brannock
Michael P. Timko