title: Growth transformation of human T cells by herpesvirus saimiri requires multiple Tip-Lck interaction motifs.
abstract: Lymphoma induction and T-cell transformation by herpesvirus saimiri strain C488 depends on two viral oncoproteins, StpC and Tip. The major interaction partner of Tip is the protein tyrosine kinase Lck, a key regulator of T-cell activation. The Lck binding domain (LBD) of Tip comprises two interaction motifs, a proline-rich SH3 domain-binding sequence (SH3B) and a region with homology to the C terminus of Src family kinase domains (CSKH). In addition, biophysical binding analyses with purified Lck-SH2 domain suggest the phosphorylated tyrosine residue 127 of Tip (pY127) as a potential third Lck interaction site. Here, we addressed the relevance of the individual binding motifs, SH3B, CSKH, and pY127, for Tip-Lck interaction and for human T-cell transformation. Both motifs within the LBD displayed Lck binding activities and cooperated to achieve a highly efficient interaction, while pY127, the major tyrosine phosphorylation site of Tip, did not enhance Lck binding in T cells. Herpesvirus saimiri strain C488 recombinants lacking one or both LBD motifs of Tip lost their transforming potential on human cord blood lymphocytes. Recombinant virus expressing Tip with a mutation at position Y127 was still able to transform human T lymphocytes but, in contrast to wild-type virus, was strictly dependent on exogenous interleukin-2. Thus, the strong Lck binding mediated by cooperation of both LBD motifs was essential for the transformation of human T cells by herpesvirus saimiri C488. The major tyrosine phosphorylation site Y127 of Tip was particularly required for transformation in the absence of exogenous interleukin-2, suggesting its involvement in cytokine signaling pathways.
authors.affiliation: Institut für Klinische und Molekulare Virologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Schlossgarten 4, D-91054 Erlangen, Germany.
authors.forename: Elke
authors.initials: E
authors.lastname: Heck
authors.forename: Ute
authors.initials: U
authors.lastname: Friedrich
authors.forename: Michaela U
authors.initials: MU
authors.lastname: Gack
authors.forename: Doris
authors.initials: D
authors.lastname: Lengenfelder
authors.forename: Monika
authors.initials: M
authors.lastname: Schmidt
authors.forename: Ingrid
authors.initials: I
authors.lastname: Müller-Fleckenstein
authors.forename: Bernhard
authors.initials: B
authors.lastname: Fleckenstein
authors.forename: Armin
authors.initials: A
authors.lastname: Ensser
authors.forename: Brigitte
authors.initials: B
authors.lastname: Biesinger
mesh_terms: D020816:Amino Acid Motifs; D002460:Cell Line; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D006567:Herpesvirus 2, Saimiriine / Q000235:genetics / Q000502:physiology*; D006801:Humans; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000737:chemistry / Q000378:metabolism*; D009154:Mutation; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011995:Recombination, Genetic; D017384:Sequence Deletion; D013601:T-Lymphocytes / Q000166:cytology / Q000821:virology*; D014443:Tyrosine / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D010750:Phosphoproteins; D014764:Viral Proteins; C092384:tyrosine kinase interacting protein, Saimiriine herpesvirus 2; D014443:Tyrosine; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)