Worm Breeder's Gazette 11(5): 29
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
We previously (WBG 11 #2, p.31) described the isolation and initial characterization of an EF2-L gene that maps about 50kb from the ubq-1 locus on chromosome III. We argued that due to the relatively low degree of amino acid sequence identity (of the region sequenced) to the eukaryotic EF-2's, the EF2-L gene (henceforth to be named eft-1) product is not likely to code for the C. elegans EF-2. Here we report further sequence analysis of eft-1 and the isolation of a C. elegans EF-2 cDNA. Complete sequencing of the 3.5 kb EF2-L gene and partial sequencing of the cDNA revealed 5 exons separated by short introns of about 46-75 base pairs. The 2547 bp open reading frame codes for an 849 amino acid polypeptide with Mr=95 kD. Comparative studies revealed 3 regions (G-regions) in the amino-terminal quarter of EF2-L which show homology with GTP-binding proteins including protein synthesis elongation and initiation factors, transducin, and mammalian RAS proteins. The carboxyl terminal half contains several conserved regions (E-regions) that are shared only among elongation factors. Similarity ranges between 48-92% and 47-58% in the G and E- regions, respectively. The overall amino acid sequence identity to eukaryotic EF-2's is 38%. The histidine (*) residue target for ADP- ribosylation by Diphtheria toxin, which is highly conserved in all eukaryotic EF-2's so far studied, is replaced by tyrosine in EF2-L; identity between EF2-L and hamster EF-2 in this region (see figure below) is greater than 55%. We carried out PCR analyses using oligonucleotides made from highly conserved regions between the hamster and Drosophila EF-2's and isolated both genomic and possibly full-length cDNA clones encoding C. elegans EF-2. The deduced amino acid sequence from the complete cDNA sequence shows a greater than 80% identity to the hamster, Drosophila, rat, human and yeast EF-2's. Developmental profiles of gene expression reveal that C. elegans EF-2 and EF2-L mRNAs (both about 3.0kb) are expressed at all stages of development. Both genes are unique and the overall amino acid sequence identity between the proteins is 34%. The function of the eft-1 gene product is unknown. The data so far suggest that it is a GTP-binding protein which may or may not be involved in the protein synthesis elongation process. If it can function in the latter capacity for general protein synthesis, one would predict that C. elegans cells would be resistant to Diphtheria toxin, since EF2-L lacks the modifiable histidine target of that enzyme. [See Figure 1]