Role for E2F1 in p210 BCR-ABL downstream regulation of c-myc transcription initiation. Studies in murine myeloid cells.
Experiments were performed to elucidate the mechanism through which p210 BCR-ABL, by its downstream signals, regulates c-myc messenger RNA expression in hematopoietic cells. We studied a model system in which stable expression of p210 BCR-ABL in interleukin-3 (IL-3) dependent murine myeloid cell lines led to growth factor independent transformation. Active c-myc transcription was observed in p210 BCR-ABL transformed cells by nuclear run-on assay, and in heterologous reporter assays performed with the 5' regulatory region of murine c-myc linked to firefly luciferase. Transcription initiation occurred primarily from the P2 promoter in p210 BCR-ABL transformed cells. Cis and trans elements responsible for transcription initiation from the c-myc P2 promoter were studied. Expression of E2F1 protein in p210 BCR-ABL transformed cells accounted, in part, for binding to the E2F site of the P2 c-myc promoter. The functional importance of E2F1 expression in p210 BCR-ABL transformed cells toward c-myc transcription was established in reporter assays performed with the P2 c-myc promoter containing either wild-type or mutant E2F sites. Mutation of the E2F motif of P2 5' c-myc reduced activity of the promoter by 50%. By gel mobility shift, E2F1 was found in P2 c-myc band shift complexes along with the cyclin-dependent kinase 2. Therefore, coupling of E2F to components of the retinoblastoma-cyclin pathway defines a route from p210 BCR-ABL to c-myc transcription, which is required for p210 BCR-ABL transformation.
Stewart
M J
MJ
Division of Hematology/Oncology, Indiana University School of Medicine, Indianapolis, USA.
Litz-Jackson
S
S
Burgess
G S
GS
Williamson
E A
EA
Leibowitz
D S
DS
Boswell
H S
HS
D000818:Animals; D001483:Base Sequence; D001667:Binding, Competitive; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002461:Cell Line, Transformed; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D016044:Fusion Proteins, bcr-abl; D017930:Genes, Reporter; D016259:Genes, myc / Q000235:genetics*; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
C533431:Arid4a protein, mouse; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493754:E2f1 protein, mouse; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D004247:DNA; D008156:Luciferases; D016044:Fusion Proteins, bcr-abl