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Title: Isolation and characterisation of Arabidopsis E2F transcription factors
Author: Jager, S. M. de
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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The present work shows that the maize Rb homologue, ZmRb, interacts with human E2F1, Drosophila dE2F and the Drosophila dE2F/dDP heterodimer, while this activity is absent from a ZmRb mutant. Genomic and cDNA sequences with the potential to encode Arabidopsis E2F homologues were identified in the Arabidopsis thaliana database. Amplification of Arabidopsis sequences by PCR with degenerated primers, based on the database sequence information, followed by DNA hybridisation library screening led to the isolation of cDNA sequences for three Arabidopsis E2F clones-AtE2F1, AtE2F2 and AtE2F3. Phylogenetic analysis of the AtE2F sequences indicated that the AtE2Fs are related to human E2Fs (30% - 44% identity), but form a distinct group. The structural domain organisation of the AtE2Fs is the same as for other E2Fs, with the DNA-binding domain, leucine zipper and marked box conserved. A putative Rb-binding domain was identified in the C-termini of the AtE2Fs. Preliminary characterisation of AtE2F1 has revealed that AtE2F1 activated transcription in yeast cells and that ZmRb repressed AtE2F1-mediated transactivation. Direct interaction of AtE2F1 with ZmRb, but not a ZmRb mutant, was shown. As a heterodimer with the human DP1 protein, AtE2F1 bound to the E2F-binding sites in the promoters of a putative Arabidopsis CDC6 homologue and the human dihydrofolate reductase gene. The expression of the three AtE2Fs was followed in a partially synchronised Arabidopsis cell suspension culture re-entering the cell cycle, and was found to be cell cycle-dependent, with peak expression during S phase. The isolation of three Arabidopsis E2F homologues which share characteristics with mammalian E2Fs, indicates that this aspect of cell cycle regulation has been conserved between plants and mammals.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available