The La protein in Schizosaccharomyces pombe: a conserved yet dispensable phosphoprotein that functions in tRNA maturation

• Published in: RNA (Cambridge) 1997-12, Vol.3 (12), p.1434-1443
• Main Authors: Van Horn, D J, Yoo, C J, Xue, D, Shi, H, Wolin, S L
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Autoantigens - genetics; Carrier Proteins - genetics; Carrier Proteins - physiology; Cytoskeletal Proteins; Fungal Proteins - genetics; Fungal Proteins - metabolism; Fungal Proteins - physiology; Humans; Molecular Sequence Data; Phosphoproteins - genetics; Phosphoproteins - metabolism; Phosphoproteins - physiology; Phosphorylation; Recombinant Fusion Proteins; Restriction Mapping; Ribonucleoproteins - genetics; RNA Processing, Post-Transcriptional - genetics; RNA, Fungal - metabolism; RNA, Transfer - metabolism; RNA-Binding Proteins - genetics; RNA-Binding Proteins - metabolism; RNA-Binding Proteins - physiology; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae Proteins; Schizosaccharomyces - genetics; Sequence Homology, Amino Acid; SS-B Antigen
• ISSN: 1355-8382; 1469-9001

Most RNA polymerase III transcripts are bound immediately after synthesis by an abundant nuclear phosphoprotein known as the La autoantigen. Experiments performed in the budding yeast Saccharomyces cerevisiae have revealed that binding of the La protein to tRNA precursors is required for the endonucleolytic maturation of the 3' terminus of many tRNAs. In the absence of this protein, the 3' ends of these tRNAs are trimmed by exonucleases (Yoo CJ, Wolin SL, 1997, Cell 89:393-402). Here we report the characterization of the La protein in the fission yeast Schizosaccharomyces pombe. As was described for budding yeast, S. pombe cells lacking the La protein are viable and exhibit alterations in the pathway of pre-tRNA maturation. Introduction of either the human, S. cerevisiae, or S. pombe La protein into these cells restores the detected pattern of tRNA processing intermediates to that of wild-type cells. By performing immunoprecipitations from cells that were metabolically labeled with 32P-orthophosphate, we demonstrate that the S. pombe and S. cerevisiae La proteins, like the human La protein, are phosphorylated in vivo. Thus, although the La protein is dispensable for growth in these yeasts, both the structure of the protein and its function in pre-tRNA maturation have been highly conserved throughout evolution.