Inhibitory interaction of c-Myb and GATA-1 via transcriptional co-activator CBP

Abstract

Gene targeting experiments have revealed that transcription factors such as c-Myb and GATA-1 play crucial roles during hematopoietic di erentiation. c-Myb is necessary in the immature cells of almost every hematopoietic lineage and GATA-1 is essential for the development of the erythroid lineage. In addition, CREB-binding protein (CBP) acts as a transcriptional adapter for various transcription factors, including cMyb and GATA-1. In this paper, we show that the transcription factors c-Myb and GATA-1 each inhibit the transcriptional activity of the other and that any possible bipartite complexes c-Myb, GATA-1, and CBP could be formed, but the tripartite complex was hardly formed. The exclusive binding of GATA-1 and c-Myb to CBP is probably the molecular basis for the mutual inhibition of their transcriptional activity. Our data suggest that cross-talk between these three factors might be important for hematopoietic di erentiation and that CBP functions as a key molecule during the process.

The carbonic anhydrase I locus contains a c-Myb target promoter and modulates differentiation of murine erythroleukemia cells

“…Takahashi et al (2000) reported that c-Myb and GATA-1 interact in vitro via their DBDs using a GST-pull down assay and that these proteins could reciprocally inhibit each other's activities on synthetic promoters. It was proposed that this inhibitory effect could be due to the exclusive binding characteristics of !c-Myb and GATA-1 to CBP.…”

“…First, it is likely that interaction between c-Myb and GATA-1 may simply have different effects on different promoters since interaction between c-Myb and GATA-1 might result in different outcomes depending on promoter context. Second, Takahashi et al (2000) used two synthetic promoter fragments, one containing six tandem repeats of the Myb-binding site and the other representing a minimal GATA-1 promoter. These synthetic promoters may not reflect situations on natural promoters where Myb-and GATA-binding sites are located in the same promoter, or when they function via novel DNA sequences.…”

“…c-Myb activity can also be suppressed by direct interactions between c-Myb and other proteins such as p160/p67, ATBF1, Cyp-40 and c-Maf (Ness, 1999). More recently, it has been reported that c-Myb can physically interact with GATA-1 using in vitro binding assays and that c-Myb and GATA-1 each is able to suppress the transcription transactivating activity of the other on two synthetic promoters (Takahashi et al, 2000). Thus, depending on the promoter context, multiple protein interactions determine the ability of cMyb to regulate gene expression and may explain the ability of c-Myb to regulate some genes in a tissuespecific manner while regulating other genes in multiple hematopoietic lineages.…”

Alteration of cell adhesion and cell cycle properties of ES cells by an inducible dominant interfering Myb mutant

“…At ®rst, we con®rmed that the activated MERT could inhibit the transcriptional activation by B-Myb in the context of ES cells. ES cell clones which constitutively expressed ERT or MERT were transfected by lipofection with a Myb responsive reporter gene, 6MBS-Luc, consisting of six tandem repeats of Myb responsive elements and luciferase gene (Takahashi et al, 2000). Then, the transfected ERT and MERT clones were cultured in the presence or absence of 4-OHT.…”

“…To activate the MERT and ERT proteins, cells were cultured in the presence of 10 77 M 4-OHT (Sigma) in most experiments except luciferase assay. For luciferase analysis, 2 mg of 6MBS-Luc plasmids (Takahashi et al, 2000) was transfected with Lipofectamine 2000 (Gibco BRL, Rockville, MD, USA) in 6 well plates. 5610 78 M 4-OHT was added 24 h after the transfection and luciferase activity was analysed 48 h after the transfection.…”