Worm Breeder's Gazette 11(5): 29

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Characterization and Sequence Analysis of an Elongation Factor 2-Like (EF2-L) Gene - An Update

Esther N. Ofulue, Peter Candido and Don Jones

Figure 1

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]

Figure 1