Translation of the Saccharomyces cerevisiae tcm1 gene in the absence of a 5'-untranslated leader

• Published in: Nucleic acids research Vol. 18; no. 19; pp. 5823 - 5828
• Main Authors: MAICAS, E, SHAGO, M, FRIESEN, J. D
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 11.10.1990
• Subjects: Base Sequence; Biological and medical sciences; Drug Resistance, Microbial - genetics; Fundamental and applied biological sciences. Psychology; Genes, Fungal; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Phenotype; Polyribosomes - metabolism; Protein Biosynthesis; Ribosomal Proteins - genetics; RNA, Fungal - metabolism; RNA, Messenger - metabolism; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Translation. Translation factors. Protein processing; Trichodermin - pharmacology; Fungi; Yeast; Ribosome; Leader sequence; Structure activity relation; Translation initiation; Deletion; Ascomycetes; Mutation; Ribosomal protein; Saccharomyces cerevisiae; Thallophyta
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/18.19.5823

The role of eukaryotic 5'-untranslated messenger RNA leaders is not entirely clear, since they share little sequence similarity among each other. The importance of the leader in determining the efficiency of translation initiation was addressed here by examining the polyribosome distribution of several leader-deletion alleles of the yeast tcm1 gene (coding for ribosomal protein L3). Shortening of this 22-nucleotide leader, or complete removal of it (the first nucleotide of the mRNA becoming the A of the translation initiation codon AUG) permitted translation, albeit reduced. Further deletion of as few as the first two nucleotides of the initiation codon leads to a substantial reduction in ribosome loading, which is compatible with inefficient initiation at the next downstream, out-of-frame, AUG triplet. A second measure of translation initiation was obtained by assaying qualitatively for the production of biologically active L3 protein using growth-resistance to trichodermin. This experiment indicates that ribosomes can recognize the correct initiation codon even in the complete absence of a leader. We conclude that the 5'-untranslated leader of the yeast tcm1 gene is not essential for accurate translation initiation, but enhances its efficiency.