The product of the mammalian orthologue of the Saccharomyces cerevisiae HBS1 gene is phylogenetically related to eukaryotic release factor 3 (eRF3) but does not carry eRF3-like activity

We describe here the cloning and sequencing of human and mouse cDNAs encodi ng a putative GTP binding protein. Sequence comparison shows that these cDN As (named eRFS) are likely to represent the orthologues of the yeast Saccha romyces cerevisiae HBS1 gene and that the C-terminal domains of the encoded proteins share structural features with eukaryotic elongation factor eEF-1 A and release factor 3 (eRF3) families. The phylogenetic analysis suggests that eRFS proteins and Hbs1p form a cluster of orthologous sequences branch ing with the eRF3 family. Nevertheless, in yeast, the human eRFS protein an d Hbs1p do not complement eRF3/Sup35p thermosensitive mutation and do not i nteract with eRF1. (C) 1998 Federation of European Biochemical Societies.