Phosphorylation of Mammalian Eukaryotic Translation Initiation Factor 6 and Its Saccharomyces cerevisiae Homologue Tif6p: Evidence that Phosphorylation of Tif6p Regulates Its Nucleocytoplasmic Distribution and Is Required for Yeast Cell Growth†
AUTOR(ES)
Basu, Uttiya
FONTE
American Society for Microbiology
RESUMO
The synthesis of 60S ribosomal subunits in Saccharomyces cerevisiae requires Tif6p, the yeast homologue of mammalian eukaryotic translation initiation factor 6 (eIF6). In the present work, we have isolated a protein kinase from rabbit reticulocyte lysates on the basis of its ability to phosphorylate recombinant human eIF6. Mass spectrometric analysis as well as antigenic properties of the purified kinase identified it as casein kinase I. The site of in vitro phosphorylation, which is highly conserved from yeast to mammals, was identified as the serine residues at positions 174 (major site) and 175 (minor site). The homologous yeast protein Tif6p was also phosphorylated in vivo in yeast cells. Mutation of Tif6p at serine-174 to alanine reduced phosphorylation drastically and caused loss of cell growth and viability. When both Ser-174 and Ser-175 were mutated to alanine, phosphorylation of Tif6p was completely abolished. Furthermore, while wild-type Tif6p was distributed both in nuclei and the cytoplasm of yeast cells, the mutant Tif6p (with Ser174Ala and Ser175Ala) became a constitutively nuclear protein. These results suggest that phosphorylatable Ser-174 and Ser-175 play a critical role in the nuclear export of Tif6p.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=180954Documentos Relacionados
- The Saccharomyces cerevisiae translation initiation factor Tif3 and its mammalian homologue, eIF-4B, have RNA annealing activity.
- The Saccharomyces cerevisiae Homologue of Mammalian Translation Initiation Factor 6 Does Not Function as a Translation Initiation Factor†
- The Saccharomyces cerevisiae TIF6 Gene Encoding Translation Initiation Factor 6 Is Required for 60S Ribosomal Subunit Biogenesis
- SUI1/p16 is required for the activity of eukaryotic translation initiation factor 3 in Saccharomyces cerevisiae.
- Phosphorylation of Eukaryotic Translation Initiation Factor 4E Is Critical for Growth