Expression of the gene encoding a translational elongation factor 3 homolog of Chlorella virus CVK2

A gene encoding a putative translational elongation factor 3 (EF-3) on the genome of Chlorella virus CVK2 has been cloned and sequenced. It encodes for a predicted polypeptide of 1120 amino acids (aa) with a molecular mass of 127 kDa. The overall amino acid sequence of CVK2 EF-3 (vEF-3) showed 36.1% identity and 83.6% similarity to that of Saccharomyces cerevisiae EF-3. Functional domains including two sets of ATP-binding motifs were extremely well conserved between vEF-3 and yeast EF-3; 63.6% identity and 92.4% similarity in total 330-aa portions. Northern blot analysis indicated that the vEF-3 gene was transcribed in the host cells early, at 20 min postinfection (p.i.), as well as late, 3-4 hr p.i. Western blot analyses with anti-vEF-3 antibody detected the 120 kDa vEF-3 protein product after 40 min p.i. It was present until the final stages of infection but absent in the virion. The vEF-3 gene was highly conserved among all Chlorella viruses isolated in Japan.