Transcription regulation by murine B-myb is distinct from that by c-myb

• Published in: Nucleic acids research 1993-01, Vol.21 (2), p.267-272
• Main Authors: Watson, R. J., Robinson, C., Lam, E. W.
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Animals; Base Sequence; Binding Sites; Biological and medical sciences; Cell Cycle Proteins; Cloning, Molecular; DNA; DNA-Binding Proteins - metabolism; Electrophoresis, Polyacrylamide Gel; Fundamental and applied biological sciences. Psychology; Fungal Proteins - genetics; Fungal Proteins - metabolism; Gene Expression Regulation; Genes, myc; Humans; Mice; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Promoter Regions, Genetic; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins c-myb; Saccharomyces cerevisiae Proteins; Simian virus 40; Simian virus 40 - genetics; Trans-Activators; Transcription Factors - genetics; Transcription Factors - metabolism; Transcription, Genetic; Transcription. Transcription factor. Splicing. Rna processing; Transcriptional Activation
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/21.2.267

The transcription regulatory properties of murine B-myb protein were compared to those of c-myb. Whereas c-Myb trans-activated an SV40 early promoter containing multiple copies of an upstream c-Myb DNA blndlng site (MBS-1), and similarly the human c-myc promoter, B-Myb was unable to do so. Full-length B-Myb translated in vitro did not bind MBS-1; however, truncation of the B-Myb C-terminus or fusion of the B-Myb DNA-binding domain to the c-Myb C-terminus showed that it was Inherently competent to Interact with this motif. Further evidence from co-transfectlon experiments, demonstrating that B-Myb Inhibited trans-activation by c-Myb, suggested that failure of B-Myb to trans-activate these promoters did not simply occur through lack of binding to MBS-1. Moreover, using GAL4B-Myb fusions, it was found that an acidic region of B-Myb, which by comparison to c-Myb was expected to contain a transcription activation domain, actually had no Inherent trans-activation activity and indeed appeared to trans-Inhibit c-Myb. In contrast to the above findings, both B-Myb and c-Myb were able to weakly trans-activate the DNA polymerase alpha promoter. Results obtained here demonstrate that the activities of B-Myb and c-Myb are clearly distinct and suggest that these related proteins may have different functions In regulation of target gene expression.