eRF3 translation termination factors: from yeast to mammals.
Oleg Tarasov (1), Vadim Schepachev (1), Alexandra Petrova (1), Svetlana Moskalenko (1), Alexej Kostygov (2), Ekaterina Rodchenkova (2), Natalia Abramson (2), Galina Zhouravleva (1)
(1) Dept. of Genetics and Breeding, St.Petersburg State University, Universitetskaja 7/9, St. Petersburg, 199034, Russian Federation; (2) Zoological Institute, Russian Academy of Sciences, Universitetskaya emb. 1, St. Petersburg, 199034, Russian Federation
Eukaryotic system for translation termination implies two factors: eRF1 and eRF3. Comparison of eRF3 orthologues in eukaryotes revealed that this protein has an N-terminal part of varying length and amino acid sequence and a C-terminal domain that is highly conserved, with strong similarity to elongation factor eEF-1alpha. Yeast gene SUP35 encoding eRF3 factor is necessary for viability. In mammals eRF3 is represented by two related proteins: eRF3a and eRF3b, each coded by a distinct gene, GSPT1 and GSPT2 respectively. These genes differ by several regions in N-domains which are conserved through evolution. It should be mentioned that GSPT2 gene is intronless. It was established that mouse GSPT2 but not GSPT1 can substitute SUP35 gene in yeast. This ability depends on the sequence of N-domain. We suppose that GSPT2 appeared in evolution by process of retroposition of ancestor eRF3 mRNA. In this work we tried to find an ancestor eRF3 gene, which could have given rise to GSPT1 and GSPT2, and a point of divergence between these two genes. Also we have studied sequences coding for N-terminal domain of eRF3b in several rodent species. It would be possible to make fusion constructs of this fragments and the part of SUP35 coding for C-terminal domain for subsequent study of their ability to substitute SUP35 in yeast. This work was supported by RFBR (03-04-48886; 03-04-49179), by CRDF and Ministry of Education RF (ST-012-0) and by the RAS program 'Biosphere origin and evolution'.