The conserved DNA binding domain mediates similar regulatory interactions for A-Myb, B-Myb, and c-Myb transcription...

The vertebrate A-Myb, B-Myb, and c-Myb proteins comprise a family of related transcription factors that share a highly conserved DNA binding domain. Although all three proteins are capable of binding the same sites in DNA, they have distinct, but overlapping patterns of expression and are presumed to be regulated independently. Here we show that the transcriptional activity of all three vertebrate Myb proteins can be severely inhibited by coexpression of a dominant-negative allele of p100, a coactivator protein that interacts with Myb DNA binding domains. Thus, the conserved Myb domains mediate interactions with common sites in DNA, as well as common regulators, suggesting that the proteins provide alternative or complementary responses to common upstream signaling pathways.