Abstract
iASPP is an inhibitory member of apoptosis-stimulating proteins of p53 (ASPP) family, which inhibits p53-dependent apoptosis. iASPP was highly expressed in acute leukemia, inhibited leukemia cells apoptosis and promoted leukemogenesis. In order to clarify its mechanism, a yeast two-hybrid screen was performed and FHL2 was identified for the first time as one of the binding proteins of iASPP. FHL2 was highly expressed in K562 and Kasumi-1 cells. FHL2 and iASPP interacted with each other and co-localized in both nucleus and cytoplasm. Either FHL2 or iASPP silenced could reduce cell proliferation, induce cell cycle arrest at G0/G1 phase, and increase cell apoptosis. Western blot analysis showed that the level of p21 and p27 increased, CDK4, E2F1, Cyclin E and anti-apoptotic proteins Bcl-2 and Bcl-xL reduced. Interestingly, when FHL2 was knocked down, the protein expression level of iASPP also decreased. Similarly, the expression of FHL2 would reduce when iASPP was silenced. These results indicated that FHL2 might be a novel potential target for acute myelocytic leukemia treatment.
Highlights
Leukemia is usually caused by genetic translocations, gene overexpression and gene mutations
The results showed that Four and a half LIM domains 2 (FHL2) could co-immunoprecipitate with inhibitory member of ASPP family (iASPP) in K562 and Kasumi-1 cells (Figure 1B)
Our previous study showed that iASPP was highly expressed in leukemia patients than that of normal controls [6], down-regulation of iASPP expression in leukemia cells by RNA interference could induce p53-dependent apoptosis of leukemia cells [25], over-expression of iASPP in transgenic mice model could increase the population, self-renewal capacity, resistance to irradiation and chemotherapy of hematopoietic stem cells [7]
Summary
Leukemia is usually caused by genetic translocations, gene overexpression and gene mutations. It is known that p53 is one of the most common mutant genes in human cancer, only 10-15% of p53 mutations were found in leukemia [1]. ASPP1, ASPP2 and iASPP belong to apoptosisstimulating proteins of p53 (ASPP) family [2]. The three members of ASPP family can interact with p53 and modulate its behavior. ASPP1 and ASPP2 enhance the ability of p53 to induce apoptosis [3, 4], iASPP is an inhibitory member of ASPP, which inhibits p53-dependent apoptosis [5]. Our previous study revealed that iASPP was highly expressed in patients with acute leukemia (AL) [6]. In order to clarify the mechanism of iASPP in leukemogenesis and looking for its cooperating partner, a yeast two-hybrid screen was performed, and FHL2 was identified as a novel binding partner of iASPP
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