Spi-1/PU.1 is a positive regulator of the Fli-1 gene involved in inhibition of erythroid differentiation in friend erythroleukemic cell lines.
Spi-1/PU.1 and Fli-1 are two members of the ETS family of transcription factors whose expression is deregulated by proviral insertion in most erythroleukemic cell lines induced by the spleen focus-forming virus (SFFV) and Friend murine leukemia virus (F-MuLV) components of the Friend viral complex, respectively. In this study, we present evidence that transcription of the Fli-1 gene is positively regulated by Spi-1/PU.1 in SFFV-transformed cell lines: (i) all SFFV-transformed cell lines expressing Spi-1/PU.1 are characterized by a specific pattern of Fli-1 gene transcripts initiated in the -200 region instead of position -400 as reported for F-MuLV-transformed cell lines; (ii) these Fli-1 transcripts initiated in the -200 region are downregulated in parallel with that of Spi-1/PU.1 during hexamethylenebisacetamide (HMBA) induced differentiation; and (iii) Fli-1 transcription is upregulated in SFFV cells lines following stable transfection of a Spi-1/PU.1 expression vector. Furthermore, we found by transient transfection assays that the -270/-41 region of the Fli-1 gene displays promoter activity which is transactivated by Spi-1/PU.1. This promoter is strictly dependent on the integrity of two highly conserved ETS DNA binding sites that bind the Spi-1/PU.1 protein in vitro. Finally, we show that transfection of constitutive or inducible Fli-1 expression vectors in SFFV-transformed cells inhibits their erythroid differentiation induced by HMBA. Overall, these data indicate that Fli-1 is a target gene of the Spi-1/PU.1 transcription factor in SFFV-transformed cell lines. We further suggest that deregulated synthesis of Fli-1 may trigger a common mechanism contributing to erythroleukemia induced by either SFFV or F-MuLV.
Starck
J
J
Centre de Génétique Moléculaire et Cellulaire, CNRS UMR 5534, 69622 Villeurbanne, France.
Doubeikovski
A
A
Sarrazin
S
S
Gonnet
C
C
Rao
G
G
Skoultchi
A
A
Godet
J
J
Dusanter-Fourt
I
I
Morle
F
F
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002461:Cell Line, Transformed; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D015672:Erythroid Precursor Cells / Q000166:cytology*; D004920:Erythropoiesis; D005622:Friend murine leukemia virus; D005786:Gene Expression Regulation; D006801:Humans; D004915:Leukemia, Erythroblastic, Acute; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D051789:Proto-Oncogene Protein c-fli-1; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D013155:Spleen Focus-Forming Viruses / Q000235:genetics; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D014981:Xenopus; D000099232:Proto-Oncogene Protein Spi-1
D004268:DNA-Binding Proteins; D051789:Proto-Oncogene Protein c-fli-1; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D000099232:Proto-Oncogene Protein Spi-1; C497426:Fli1 protein, mouse