In Xenopus laevis, the product of a developmentally regulated mRNA is structurally and functionally homologous to a Saccharomyces cerevisiae protein involved in translation fidelity.
We have performed a differential screen of a Xenopus egg cDNA library and selected two clones (Cl1 and Cl2) corresponding to mRNA which are specifically adenylated and recruited into polysomes after fertilization. Sequence analysis of Cl1 reveals that the corresponding protein is 67.5% identical (83% similar) to the product of the Saccharomyces cerevisiae SUP45 (also called SUP1 or SAL4) gene. This gene, when mutated, is an omnipotent suppressor of nonsense codons. When expressed in a sup45 mutant, the Xenopus Cl1 cDNA was able to suppress sup45-related phenotypes, showing that the structural homology reflects a functional homology. Our discovery of a structural and functional homolog in Xenopus cells implies that the function of SUP45 is not restricted to lower eukaryotes and that the SUP45 protein may perform a crucial cellular function in higher eukaryotes.
Tassan
J P
JP
Département de Biologie et Génétique du Développement, CNRS URA 256, Université de Rennes I, France.
Le Guellec
K
K
Kress
M
M
Faure
M
M
Camonis
J
J
Jacquet
M
M
Philippe
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000502:physiology; D004247:DNA / Q000235:genetics* / Q000302:isolation & purification; D004527:Egg Proteins / Q000235:genetics*; D004625:Embryo, Nonmammalian / Q000502:physiology; D005260:Female; D005306:Fertilization; D005656:Fungal Proteins / Q000235:genetics*; D005786:Gene Expression Regulation; D015723:Gene Library; D005800:Genes, Fungal; D006321:Heart / Q000502:physiology; D008099:Liver / Q000502:physiology; D008297:Male; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D010454:Peptide Termination Factors; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D013489:Suppression, Genetic; D013737:Testis / Q000502:physiology; D014982:Xenopus laevis / Q000196:embryology / Q000235:genetics*
C080776:49 kDa protein, Xenopus; D004527:Egg Proteins; D005656:Fungal Proteins; D010454:Peptide Termination Factors; D012333:RNA, Messenger; C080775:SUP45 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D004247:DNA