Activation of c-myc expression by c-Abl is independent of both the DNA binding function of c-Abl and the c-myc EP site.
We have shown by transient transfection assays that c-Abl increases expression of a c-myc promoter construct although to a lesser extent than v-Abl. c-Abl has been reported to bind to a specific DNA sequence, the EP element, in the hepatitis B virus enhancer. A similar sequence exists in the promoter region of the c-myc gene, and we have identified a potential protein binding site in this region by in vivo footprinting. Gel shift analysis demonstrated that the hepatitis B virus enhancer and c-myc sites yield identical complexes. To determine whether c-Abl activates c-myc transcription by binding directly to the promoter region, several experiments were performed. Mutation of the EP site in the c-myc promoter had no effect on transcriptional activation of c-myc by c-Abl. Next, we demonstrated that the DNA binding domain of c-Abl was not required for the transcriptional activation of c-myc. Finally, by Western blot analysis, we have determined that c-Abl is not present in the gel shift complexes formed by either the hepatitis B virus enhancer or c-myc promoter. We conclude that c-Abl activates c-myc transcription indirectly with no requirement for DNA binding by c-Abl. We also find no evidence for the interaction of c-Abl with the EP sequence of either the hepatitis B virus enhancer or the c-myc promoter.
Arcinas
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M
Center for Molecular Biology in Medicine, Palo Alto Veterans Administration Medical Center, California.
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D001483:Base Sequence; D002478:Cells, Cultured; D003432:Cross-Linking Reagents; D004252:DNA Mutational Analysis; D005786:Gene Expression Regulation / Q000235:genetics*; D016259:Genes, myc / Q000235:genetics*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D016315:Proto-Oncogene Proteins c-abl / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis* / Q000235:genetics; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D014158:Transcription, Genetic; D014466:Ultraviolet Rays
D003432:Cross-Linking Reagents; D009687:Nuclear Proteins; D016271:Proto-Oncogene Proteins c-myc; D016315:Proto-Oncogene Proteins c-abl