The p53 tumor suppressor protein plays a crucial role in tumorigenesis by controlling cell-cycle progression and apoptosis. We have previously described a transcript designated tumor suppressor activated pathway-6 (TSAP6) that is up-regulated in the p53-inducible cell line, LTR6. Cloning of the murine and human fulllength TSAP6 cDNA revealed that it encodes a 488-aa protein with five to six transmembrane domains. This gene is the murine and human homologue of the recently published rat pHyde. Antibodies raised against murine and human TSAP6 recognize a 50-to 55-kDa band induced by p53. Analysis of the TSAP6 promoter identified a functional p53-responsive element. Functional studies demonstrated that TSAP6 antisense cDNA diminished levels of the 50-to 55-kDa protein and decreased significantly the levels of p53-induced apoptosis. Furthermore, TSAP6 small interfering RNA inhibited apoptosis in TSAP6-overexpressing cells. Yeast two-hybrid analysis followed by GST͞in vitro-transcribed͞translated pulldown assays and in vivo coimmunoprecipitations revealed that TSAP6 associated with Nix, a proapoptotic Bcl-2-related protein and the Myt1 kinase, a negative regulator of the G 2͞M transition. Moreover, TSAP6 enhanced the susceptibility of cells to apoptosis and cooperated with Nix to exacerbate this effect. Cell-cycle studies indicated that TSAP6 could augment Myt1 activity. Overall, these data suggest that TSAP6 may act downstream to p53 to interface apoptosis and cell-cycle progression.

In this study, we explored the telomeric changes that occur in B-chronic lymphocytic leukemia (B-CLL), in which telomere length has recently been demonstrated to be a powerful prognostic marker. We carried out a transcriptomic analysis of telomerase components (hTERT and DYSKERIN), shelterin proteins (TRF1, TRF2, hRAP1, TIN2, POT1, and TPP1), and a set of multifunctional proteins involved in telomere maintenance (hEST1A, MRE11, RAD50, Ku80, and RPA1) in peripheral B cells from 42 B-CLL patients and 20 healthy donors. We found that, in B-CLL cells, the expressions of hTERT, DYSKERIN, TRF1, hRAP1, POT1, hEST1A, MRE11, RAD50, and KU80 were more than 2-fold reduced (P < .001), contrasting with the higher expression of IntroductionTelomeres are nucleoprotein structures that cap chromosomes and shorten with each division. Telomere structure and functions depend on the telomerase enzyme (hTERT, hTR, DYSKERIN) for elongation, 1 on the shelterin complex (TRF1, TRF2, TIN2, hRAP1, TPP1, POT1) that regulates telomere length and protects them against degradation and fusion, and on a set of multifunctional factors, including RPA1, hEST1A, KU70/KU80 and the RAD50-MRE11-NBS1 complex 2 ( Figure 1A).Telomerase activity is absent or very low in somatic cells and increased in proliferative lymphoid cells. 3 In most cancer cells, the catalytic subunit of telomerase (hTERT) is overexpressed to allow their long-term proliferation. 4 Research in oncogenesis is now focusing on the other telomeric genes, especially the shelterin complex. [5][6][7][8][9][10] Specific changes in the expression of these genes in cancers may provide new knowledge about oncogenesis and useful clinical markers, but would also lead to the development of new therapeutic agents.B-cell chronic lymphocytic leukemia (B-CLL) results from the progressive accumulation of a leukemic clone (for review, see Chiorazzi and Ferrarini 11 ) that shows lower telomerase activity at disease onset 12 and increased activity in advanced stages and bad prognosis group. 13 Telomeres are shorter in B-CLL cells versus normal B cells, and especially short for patients with bad prognosis. Telomere length is thus a powerful prognostic marker for B-CLL. 13,14 In this work, we investigated whether the transcriptional status of the telomeric proteins is modified in B cells from B-CLL patients. Methods Isolation of human B cellsAfter consent was obtained in accordance with the Declaration of Helsinki and according to institutional guidelines, total blood samples were collected from 20 healthy donors (at the "Etablissement Français du Sang" of Lyon and Pitié-Salpétrière Hospital) and from 42 B-CLL patients (at the Lyon Sud and Pitié-Salpétrière Hospitals). Diagnoses were confirmed using morphology and flow-cytometry usual B-CLL characteristics (Matutes score Ն 4). B lymphocytes were purified from peripheral blood by negative selection using the RosetteSep Human B-cell enrichment cocktail (Stem Cell Technologies, Vancouver, BC). The percentage of CD19 ϩ cells was determined by cytometric assay ...