Oxidative stress promotes transcriptional up-regulation of Fyn in BCR-ABL1-expressing cells.
Signaling initiated by the BCR-ABL1 kinase causes chronic myelogenous leukemia (CML). Recently, we reported that expression of Fyn, a Src kinase, is heightened in CML cells and patient specimens and confers in vitro and in vivo proliferative advantages. Fyn is regulated by redox, and because BCR-ABL1 raises intracellular oxidant levels, which have been implicated in CML progression, we explored the molecular regulation of Fyn. Here we identify the transcription factors that drive redox- and BCR-ABL1-dependent Fyn expression. Promoter deletion analysis in 293T, BaF3, BaF3-p210, and K562 cells identified the region essential for basal transcriptional activity. Mutation of Sp1 and Egr1 binding sites within the essential region diminished Fyn promoter activity and identified Egr1 as conferring redox sensitivity. Gel shift and chromatin immunoprecipitation assays confirmed the binding of Sp1 and Egr1 to the promoter fragments. Importantly, knockdown of Sp1 or Egr1 with small interference RNA or inhibition of Sp1 binding by mithramycin A repressed Fyn protein expression. Our work is the first to define transcription factors that are responsible for endogenous, oxidative stress-dependent and BCR-ABL1-dependent Fyn expression.
Gao
Yin
Y
Department of Pediatrics Research, Unit 853, Children's Cancer Hospital at M. D. Anderson, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Howard
Adrienne
A
Ban
Kechen
K
Chandra
Joya
J
D051766:Early Growth Response Protein 1 / Q000235:genetics / Q000378:metabolism; D016044:Fusion Proteins, bcr-abl / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020014:K562 Cells; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology*; D051076:Proto-Oncogene Proteins c-fyn / Q000096:biosynthesis* / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D020218:Response Elements / Q000502:physiology*; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology*; D015854:Up-Regulation / Q000502:physiology*
C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D034741:RNA, Small Interfering; D016329:Sp1 Transcription Factor; C494957:FYN protein, human; D016044:Fusion Proteins, bcr-abl; D051076:Proto-Oncogene Proteins c-fyn