Evolutionary conservation of nuclear and nucleolar targeting sequences in yeast ribosomal protein S6A.
Over 1 billion years ago, the animal kingdom diverged from the fungi. Nevertheless, a high sequence homology of 62% exists between human ribosomal protein S6 and S6A of Saccharomyces cerevisiae. To investigate whether this similarity in primary structure is mirrored in corresponding functional protein domains, the nuclear and nucleolar targeting signals were delineated in yeast S6A and compared to the known human S6 signals. The complete sequence of S6A and cDNA fragments was fused to the 5'-end of the LacZ gene, the constructs were transiently expressed in COS cells, and the subcellular localization of the fusion proteins was detected by indirect immunofluorescence. One bipartite and two monopartite nuclear localization signals as well as two nucleolar binding domains were identified in yeast S6A, which are located at homologous regions in human S6 protein. Remarkably, the number, nature, and position of these targeting signals have been conserved, albeit their amino acid sequences have presumably undergone a process of co-evolution with their corresponding rRNAs.
Zentrum für Experimentelle Medizin, Institut für Molekulare Zellbiologie, Universität Hamburg, Hamburg, Germany.
Edgar
E
Lipsius
Korden
K
Walter
Torsten
T
Leicher
Wolfgang
W
Phlippen
Marc-Angelo
MA
Bisotti
Joachim
J
Kruppa
D002466:Cell Nucleolus / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000235:genetics* / Q000378:metabolism*; D017124:Conserved Sequence; D019143:Evolution, Molecular; D006801:Humans; D019913:Nuclear Localization Signals / Q000235:genetics / Q000378:metabolism; D038601:Ribosomal Protein S6 / Q000235:genetics* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D016415:Sequence Alignment / Q000379:methods; D020539:Sequence Analysis, Protein / Q000379:methods*; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
D019913:Nuclear Localization Signals; D038601:Ribosomal Protein S6