Submitted on December 27, 2004
Accepted on February 7, 2005
Evolution of vertebrate E-protein transcription factors: Comparative analysis of the E-protein gene family in Takifugu rubripes and humans
Jun-ichi Hikima1, Mara L Lennard1, Melanie R Wilson2, Norman W Miller2, L. William Clem2, and Gregory W Warr1*
1 Marine Biomedicine and Environmental Sciences Center and Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA
2 Department of Microbiology, University of Mississippi Medical Center, Jackson, MS, USA
* To whom correspondence should be addressed. E-mail: warrgw{at}musc.edu.
E-proteins are essential for B lymphocyte development and function, including immunoglobulin (Ig) gene rearrangement and expression. Previous studies of B cells in the channel catfish (Ictalurus punctatus) identified E-protein homologues that are capable of binding the µE5 motif, and driving a strong transcriptional response. There are 3 E-protein genes in mammals, HEB (TCF12), E2A (TCF3), and E2-2 (TCF4). The major expressed E-proteins found in catfish B cells are homologues of HEB and of E2A. Here we sought to define the complete family of E-protein genes in a teleost fish, Takifugu rubripes, taking advantage of the completed genome sequence. The catfish CFEB (HEB homologue) sequence identified homologous E-protein encoding sequences in 5 scaffolds in the Takifugu genome database. Detailed comparative analysis with the human genome revealed the presence of 5 E-protein homologues in Takifugu. Single genes orthologous to HEB and to E2-2 were identified. In contrast, 2 members of the E2A gene family were identified in Takifugu; one of these shows the alternative processing of transcripts that identifies it as the orthologue of the E12/E47 encoding mammalian E2A gene, whereas the second Takifugu E2A gene has no predicted alternative splice products. A novel fifth E-protein gene (EX) was identified in Takifugu. Phylogenetic analysis revealed four E-protein branches among vertebrates, EX, E2A, HEB, and E2-2.
