Transcriptional activation of the c-myc gene by the c-myb and B-myb gene products.
To identify the target genes modulated by the myb gene product (Myb), a co-transfection assay with a Myb expression plasmid was performed. Both c-Myb and B-Myb, another member of the myb gene family, trans-activated the human c-myc promoter. DNAase I footprint analysis using the bacterially expressed c-Myb, identified multiple c-Myb binding sites in the c-myc promoter region. Deletion analysis of the c-myc promoter suggested that some number of Myb binding sites, not a specific Myb binding site, is important for the c-Myb-induced trans-activation of the c-myc promoter. Using the c-myc-chloramphenicol acetyltransferase (CAT) construct as a reporter in a co-transfection assay, the domains of c-Myb required for trans-activation were examined. The functional domains of c-Myb identified using the c-myc promoter were almost the same as those identified previously with the artificial target gene containing Myb binding sites, but unlike the case with the artificial target gene the N-terminal half of the previously identified negative regulatory domains and the C-terminal 136 amino acids were required for the maximal trans-activation of the c-myc promoter. These results indicate that there are some differences in the regulation of Myb-dependent trans-activation in different target genes.
Nakagoshi
H
H
Laboratory of Molecular Genetics, Tsukuba Life Science Center, Institute of Physical and Chemical Research (RIKEN), Ibaraki, Japan.
Kanei-Ishii
C
C
Sawazaki
T
T
Mizuguchi
G
G
Ishii
S
S
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D002872:Chromosome Deletion; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016259:Genes, myc; D006801:Humans; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D009857:Oncogenes; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D020598:Proto-Oncogene Proteins c-myb; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; D009838:Oligodeoxyribonucleotides; D011518:Proto-Oncogene Proteins; D020598:Proto-Oncogene Proteins c-myb; D011993:Recombinant Fusion Proteins; D015500:Chloramphenicol O-Acetyltransferase