Apoptosis induced by the myelodysplastic syndrome-associated NPM-MLF1 chimeric protein.
The NPM-MLF1 chimeric protein is produced by the t(3;5)(q25.1;q34) chromosomal translocation, which is associated with myelodysplastic syndrome (MDS) prior to progression into acute myeloid leukemia (AML). Here we report that K562 human leukemia cells ectopically expressing NPM-MLF1, but not those with wild-type MLF1, were gradually eliminated from the culture by undergoing apoptosis. NIH3T3 mouse fibroblasts engineered to overexpress NPM-MLF1 grew normally but serum deprivation triggered apoptotic cell death with slower kinetics than did other well-known apoptotic inducers such as c-Myc or E2F-1. Quantitative analysis of apoptotic induction confirmed that, neither NPM nor MLF1, but the NPM-MLF1 fusion protein was able to induce apoptosis. Analyses using a variety of deletion mutants of NPM-MLF1 revealed that induction of apoptosis required the N-terminal domain of MLF1 and the NPM domain containing nuclear localization signal and that removal of the NPM dimerization domain markedly impaired the ability to induce apoptosis. Co-expression of Bcl-2 rescued NIH3T3 fibroblasts from NPM-MLF1-mediated cell death without affecting the expression level or the subcellular localization of NPM-MLF1 and enabled cells to progress into S phase in low serum. These findings provide an NPM-MLF1-mediated novel mechanism of apoptotic induction and imply that NPM-MLFI in collaboration with anti-apoptotic oncoproteins may play an important role in multi-step progression from MDS to AML.
First Department of Internal Medicine, Kansai Medical University, Moriguchi, Osaka, Japan.
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N
Yoneda-Kato
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S
Fukuhara
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J
Kato
D016475:3T3 Cells; D000208:Acute Disease; D000818:Animals; D017209:Apoptosis; D019556:COS Cells; D002893:Chromosomes, Human, Pair 3 / Q000235:genetics; D002895:Chromosomes, Human, Pair 5 / Q000235:genetics; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D006801:Humans; D020014:K562 Cells / Q000378:metabolism / Q000473:pathology; D007951:Leukemia, Myeloid / Q000235:genetics; D051379:Mice; D009190:Myelodysplastic Syndromes / Q000235:genetics / Q000473:pathology*; D015514:Oncogene Proteins, Fusion; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D014162:Transfection; D014178:Translocation, Genetic
D016895:Culture Media, Serum-Free; C120078:NPM-MLF1 protein, human; D015514:Oncogene Proteins, Fusion; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins