Transcriptional silencing of the ETS1 oncogene contributes to human granulocytic differentiation

Valentina Lulli, Paolo Romania, Roberta Riccioni, Alessandra Boe, Francesco Lo-Coco, Ugo Testa, Giovanna Marziali

Research output: Contribution to journalArticlepeer-review

Abstract

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.

Original languageEnglish
Pages (from-to)1633-1641
Number of pages9
JournalHaematologica
Volume95
Issue number10
DOIs
Publication statusPublished - Oct 2010

Keywords

  • Granulocytic differentiation
  • Hematopoiesis
  • Transcription factors

ASJC Scopus subject areas

  • Hematology

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