Diana S Fleckenstein

Publications (2)5.85 Total impact

• Article: Tumor necrosis factor receptor-associated factor (TRAF) 4 is a new binding partner for the p70S6 serine/threonine kinase.

  Diana S Fleckenstein, Wilhelm G Dirks, Hans G Drexler, Hilmar Quentmeier
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  ABSTRACT: p70S6K is an intracellular serine/threonine kinase that mediates cell cycle progression and gene transcription. Immunofluorescent staining shows in factor-dependent hematopoietic M-07e cells that p70S6K is localized both in the cytosol and, after cytokine stimulation, also in the nucleus. We hypothesized that the p70S6K might interact with a transcription factor in the nucleus or with other proteins in the cytosol besides the S6 protein. By screening a yeast two-hybrid HeLa cDNA library with full-length p70S6K cDNA as bait, we identified tumor necrosis factor receptor-associated factor (TRAF) 4 as a new binding partner for this kinase. TRAF4 is a member of the TRAF family of putative signal-transducing proteins. Members of this family are capable of negatively regulating apoptotic pathways by inducing the expression of genes that promote cell survival. Immunoprecipitation experiments showed that stimulation of receptors of the tumor necrosis factor (TNF) family induced the formation of TRAF4/p70S6K complexes. Transfection studies showed that TRAF4 functions in p70S6K activation: TNF induced phosphorylation of S6, the main intracellular substrate of the kinase, in cells stably expressing TRAF4, but not in TRAF4-negative cells. In addition to its role in p70S6K activation, we postulate an anti-apoptotic role for TRAF4, because the agonistic anti-Fas antibody CH-11 induced apoptosis in untransfected HEK-293 cells, but not in TRAF4-expressing HEK-293 cells. In conclusion: (i) TNF-receptor activation leads to activation of the p70S6K; (ii) TRAF4 is a mediator in this TNF-induced signaling pathway; and (iii) TRAF4 inhibits Fas-induced apoptosis.
  Leukemia Research 09/2003; 27(8):687-94. · 2.92 Impact Factor
• Article: Detection of p53 gene mutations by single strand conformational polymorphism (SSCP) in human acute myeloid leukemia-derived cell lines.

  Diana S Fleckenstein, Cord C Uphoff, Hans G Drexler, Hilmar Quentmeier
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  ABSTRACT: We have identified new mutations in the p53 gene in 3/11 growth factor-independent and in 2/8 growth factor-dependent human acute myeloid leukemia (AML)-derived cell lines by single-strand conformational polymorphism (SSCP) and sequencing analysis. MEG-01 had a triplet deletion at codon 304; F-36P, NB-4 and MV4-11 showed point mutations at codon 344. F-36P had a second point mutation at codon 270 and NB-4 additionally at codon 319. M-MOK had a nucleotide substitution at codon 191. The frequency of p53 mutations in the cytokine-independent cell lines was comparable to that in the cytokine-dependent lines. These results suggest that loss of Wild type (wt) p53 is not the decisive event causing tumor cells to proliferate in vitro without externally added growth factors.
  Leukemia Research 03/2002; 26(2):207-14. · 2.92 Impact Factor