title: High levels of the onco-protein Gfi-1 accelerate T-cell proliferation and inhibit activation induced T-cell death in Jurkat T-cells.
abstract: Gfi-1 is a nuclear zinc finger protein with the activity of a transcriptional repressor and the ability to predispose for the development of T-cell lymphoma when expressed constitutively at high levels. Whereas thymic T-cell precursors express endogenous Gfi-1, mature peripheral T-cells lack Gfi-1 but upregulate its expression transiently after antigenic stimulation and activation of Erk1/2 demonstrating a role of Gfi-1 in T-cell activation. Here we show that constitutive expression of Gfi-1 accelerates S phase entry of primary, resting T-cells upon antigenic stimulation. In addition, high level Gfi-1 expression inhibits phorbol ester induced G1 arrest and activation induced cell death in Jurkat T-cells. We demonstrate that these effects of Gfi-1 concur with lower absolute levels and hyperphosphorylation of the pocket protein pRb. Moreover, phorbol ester induced expression of the negative cell cycle regulator p21(WAF1) is blocked in the presence of Gfi-1. These findings suggest that Gfi-1 contributes to T-cell lymphomagenesis by overriding a late G1 cell cycle checkpoint which controls activation induced death and S phase entry of T-cells.
authors.affiliation: Institut für Zellbiologie (Tumorforschung), IFZ, Universitätsklinikum Essen, Virchowstrasse 173, D-45122 Essen, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Karsunky
authors.forename: Ines
authors.initials: I
authors.lastname: Mende
authors.forename: Thorsten
authors.initials: T
authors.lastname: Schmidt
authors.forename: Tarik
authors.initials: T
authors.lastname: Möröy
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism; D018801:CD2 Antigens / Q000235:genetics; D002453:Cell Cycle; D016923:Cell Death; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D007700:Kinetics; D037181:Lectins, C-Type; D008213:Lymphocyte Activation; D051379:Mice; D008822:Mice, Transgenic; D015513:Oncogene Proteins / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014157:Transcription Factors; D014158:Transcription, Genetic; D015854:Up-Regulation; D000099192:CD69 Antigens
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D018801:CD2 Antigens; D004268:DNA-Binding Proteins; D037181:Lectins, C-Type; D015513:Oncogene Proteins; D012333:RNA, Messenger; D011948:Receptors, Antigen, T-Cell; D013755:Tetradecanoylphorbol Acetate; D014157:Transcription Factors; D000099192:CD69 Antigens; C498275:GFI1 protein, human; C079873:Gfi1 protein, mouse