title: Stress-inducible, murine protein mSTI1. Characterization of binding domains for heat shock proteins and in vitro phosphorylation by different kinases.
abstract: We have recently isolated the cDNA for the murine homologue of the stress-inducible phosphoprotein STI1 (also known as IEF SSP 3521 or p60). STI1 was previously shown to be 2-fold up-regulated in MRC-5 fibroblasts upon viral transformation and to exist in a macromolecular complex with heat shock proteins of the HSP 70 and 90 families. By peptide-sequencing we have identified the two heat shock proteins that bind to murine STI1 (mSTI1) as HSC 70 and HSP 84/86. We describe two separate binding regions within mSTI1 for the two heat shock proteins. In the presence of cell extracts, the N-terminal region of mSTI1 binds preferentially to HSC 70, whereas the C-terminal portion of the molecule promotes the binding of HSP 84/86. Heat treatment caused a strong induction of mSTI1 message without affecting the steady-state level of the protein significantly. In addition, heat treatment led to changes in the isoform-composition of mSTI1. pp70(s6k), pp90(rsk), and mitogen-activated protein kinase-activated protein kinase 2 were tested as possible STI1 kinases in vitro using recombinant mSTI1 as a substrate: only pp90(rsk) was able to phosphorylate recombinant mSTI1. In vitro kinase assays using casein kinase II suggest serine 189 to be a likely phosphorylation site in mSTI1.
authors.affiliation: Department of Cell Biology and Surgery, Harvard Medical School and Children's Hospital, Boston, Massachusetts 02115, USA. lassle@mit.edu
authors.forename: M
authors.initials: M
authors.lastname: Lässle
authors.forename: G L
authors.initials: GL
authors.lastname: Blatch
authors.forename: V
authors.initials: V
authors.lastname: Kundra
authors.forename: T
authors.initials: T
authors.lastname: Takatori
authors.forename: B R
authors.initials: BR
authors.lastname: Zetter
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002457:Cell Extracts; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D005982:Glutathione Transferase / Q000235:genetics; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D002457:Cell Extracts; D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase; D011494:Protein Kinases