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pubmed:abstractText |
MicroRNAs (miRs) are small noncoding RNAs that regulate gene expression primarily through translational repression. In erythropoietic (E) culture of cord blood CD34+ progenitor cells, the level of miR 221 and 222 is gradually and sharply down-modulated. Hypothetically, this decline could promote erythropoiesis by unblocking expression of key functional proteins. Indeed, (i) bioinformatic analysis suggested that miR 221 and 222 target the 3' UTR of kit mRNA; (ii) the luciferase assay confirmed that both miRs directly interact with the kit mRNA target site; and (iii) in E culture undergoing exponential cell growth, miR down-modulation is inversely related to increasing kit protein expression, whereas the kit mRNA level is relatively stable. Functional studies show that treatment of CD34+ progenitors with miR 221 and 222, via oligonucleotide transfection or lentiviral vector infection, causes impaired proliferation and accelerated differentiation of E cells, coupled with down-modulation of kit protein: this phenomenon, observed in E culture releasing endogenous kit ligand, is magnified in E culture supplemented with kit ligand. Furthermore, transplantation experiments in NOD-SCID mice reveal that miR 221 and 222 treatment of CD34+ cells impairs their engraftment capacity and stem cell activity. Finally, miR 221 and 222 gene transfer impairs proliferation of the kit+ TF-1 erythroleukemic cell line. Altogether, our studies indicate that the decline of miR 221 and 222 during exponential E growth unblocks kit protein production at mRNA level, thus leading to expansion of early erythroblasts. Furthermore, the results on kit+ erythroleukemic cells suggest a potential role of these miRs in cancer therapy.
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pubmed:affiliation |
Department of Hematology, Oncology, and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy.
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pubmed:publicationType |
Journal Article,
Comparative Study,
Research Support, Non-U.S. Gov't,
Research Support, N.I.H., Extramural
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