TY - JOUR AU - Valentina Lulli, AU - Paolo Romania, AU - Roberta Riccioni, AU - Alessandra Boe, AU - Francesco Lo-Coco, AU - Ugo Testa, AU - Giovanna Marziali, PY - 2010/09/30 Y2 - 2024/03/28 TI - Transcriptional silencing of the ETS1 oncogene contributes to human granulocytic differentiation JF - Haematologica JA - haematol VL - 95 IS - 10 SE - Articles DO - 10.3324/haematol.2010.023267 UR - https://haematologica.org/article/view/5746 SP - 1633-1641 AB - Background Ets-1 is a widely expressed transcription factor implicated in several biological processes including hematopoiesis, where it contributes to the regulation of cellular differentiation. The functions of Ets-1 are regulated by transcription factors as well as by phosphorylation events: phosphorylation of threonine 38 activates Ets-1, whereas phosphorylation of a cluster of serines within exon VII reduces DNA binding activity. This study focuses on the role of Ets-1 during granulocytic differentiation of NB4 promyelocytic and HL60 myeloblastic leukemia cell lines induced by all-trans retinoic acid.Design and Methods Ets-1 expression was measured by real-time reverse transcriptase polymerase chain reaction and western blotting. The role of Ets-1 during all-trans retinoic acid-induced differentiation was analyzed by using a transdominant negative molecule or small interfering RNA.Results NB4 and HL60 cell lines expressed high levels of p51 Ets-1, while the splice variant isoform that lacks exon VII (p42) was almost undetectable. The addition of all-trans retinoic acid reduced p51 Ets-1 levels and induced inhibitory phosphorylation of the remaining protein. Expression of Ets-1 was also reduced during dimethylsulfoxide-induced differentiation and during granulocytic differentiation of human CD34+ hematopoietic progenitor cells but not in NB4.R2 and HL60R cells resistant to all-trans retinoic acid. In line with these observations, transduction of a transdominant negative molecule of Ets-1, which inhibited DNA binding and transcriptional activity of the wild-type Ets-1, significantly increased chemical-induced differentiation. Consistently, Ets-1 knockdown by small interfering RNA increased the number of mature neutrophils upon addition of all-trans retinoic acid. Interestingly, p51 Ets-1 over-expression was frequently observed in CD34+ hematopoietic progenitor cells derived from patients with acute myeloid leukemia, as compared to its expression in normal CD34+ cells.Conclusions Our results indicated that a decreased expression of Ets-1 protein generalizes to granulocytic differentiation and may represent a crucial event for granulocytic maturation. ER -