E2F Transcription Factor Family
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).
14 predicted putative E2F TF peptide,
CDS, and cDNA sequences;
blast HSP, and multiple sequence alignment
in Soy - TFKB.
14 E2F_TDP domain peptide sequences with alignment and phylogeny tree.
No E2F soybean protein and DNA sequences listed in
PlantTFDB.
Last updated by Dr. Jeff Chen
on July 20, 2009.
