Transcription factor SCL is required for c-kit expression and c-Kit function in hemopoietic cells.
In normal hemopoietic cells that are dependent on specific growth factors for cell survival, the expression of the basic helix-loop-helix transcription factor SCL/Tal1 correlates with that of c-Kit, the receptor for Steel factor (SF) or stem cell factor. To address the possibility that SCL may function upstream of c-kit, we sought to modulate endogenous SCL function in the CD34(+) hemopoietic cell line TF-1, which requires SF, granulocyte/macrophage colony-stimulating factor, or interleukin 3 for survival. Ectopic expression of an antisense SCL cDNA (as-SCL) or a dominant negative SCL (dn-SCL) in these cells impaired SCL DNA binding activity, and prevented the suppression of apoptosis by SF only, indicating that SCL is required for c-Kit-dependent cell survival. Consistent with the lack of response to SF, the level of c-kit mRNA and c-Kit protein was significantly and specifically reduced in as-SCL- or dn-SCL- expressing cells. c-kit mRNA, c-kit promoter activity, and the response to SF were rescued by SCL overexpression in the antisense or dn-SCL transfectants. Furthermore, ectopic c-kit expression in as-SCL transfectants is sufficient to restore cell survival in response to SF. Finally, enforced SCL in the pro-B cell line Ba/F3, which is both SCL and c-kit negative is sufficient to induce c-Kit and SF responsiveness. Together, these results indicate that c-kit, a gene that is essential for the survival of primitive hemopoietic cells, is a downstream target of the transcription factor SCL.
Krosl
G
G
Clinical Research Institute of Montreal, Montréal, Quebec H2W 1R7, Canada.
He
G
G
Lefrancois
M
M
Charron
F
F
Roméo
P H
PH
Jolicoeur
P
P
Kirsch
I R
IR
Nemer
M
M
Hoang
T
T
D051792:Basic Helix-Loop-Helix Proteins; D001854:Bone Marrow Cells / Q000378:metabolism; D002470:Cell Survival; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology; D016376:Oligonucleotides, Antisense; D011518:Proto-Oncogene Proteins; D019009:Proto-Oncogene Proteins c-kit / Q000096:biosynthesis* / Q000235:genetics; D019089:Stem Cell Factor / Q000494:pharmacology; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D007377:Interleukin-3; D016376:Oligonucleotides, Antisense; D011518:Proto-Oncogene Proteins; D019009:Proto-Oncogene Proteins c-kit; D019089:Stem Cell Factor; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; D014157:Transcription Factors; C067143:TAL1 protein, human