title: Cellular localization and phosphorylation of Hrb1p is independent of Sky1p.
abstract: Protein phosphorylation plays a major role in regulating cellular functions. We have previously demonstrated that Sky1p, the SR protein kinase of the budding yeast Saccharomyces cerevisiae, is a regulator of polyamine transport and ion homeostasis. Since its kinase activity was demonstrated essential for fulfilling these roles, we assumed that Sky1p function via substrates phosphorylation. Using an in vitro phosphorylation assay, we have identified Hrb1p as a putative Sky1p substrate. However, phosphorylation analysis in WT and sky1Delta cells and localization studies disproved Hrb1p as a true Sky1p substrate, although a segment of the RS domain is required for determining its subcellular localization. Furthermore, we demonstrate that Hrb1p and additional putative Sky1p substrates, identified by computational approach, are not involved in mediating the spermine tolerant phenotype of sky1Delta cells.
authors.affiliation: Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, ISRAEL.
authors.forename: Ziv
authors.initials: Z
authors.lastname: Porat
authors.forename: Omri
authors.initials: O
authors.lastname: Erez
authors.forename: Chaim
authors.initials: C
authors.lastname: Kahana
mesh_terms: D000409:Alanine / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D002467:Cell Nucleus / Q000378:metabolism*; D019295:Computational Biology; D003593:Cytoplasm / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D005800:Genes, Fungal; D049452:Green Fluorescent Proteins / Q000378:metabolism; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D029543:Nucleocytoplasmic Transport Proteins; D010766:Phosphorylation; D010957:Plasmids; D039102:Poly(A)-Binding Proteins; D011494:Protein Kinases / Q000032:analysis; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D013379:Substrate Specificity
chemical_list: D005656:Fungal Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins; C089362:Hrb1 protein, S cerevisiae; D029543:Nucleocytoplasmic Transport Proteins; D039102:Poly(A)-Binding Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; D011494:Protein Kinases; C490216:SKY1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D000409:Alanine