TRANSACTIVATION AND TRANSFORMATION BY MYB ARE NEGATIVELY REGULATED BYA LEUCINE-ZIPPER STRUCTURE

The negative regulatory domain of the c-myb protooncogene product (c-M yb) normally represses transcriptional activation by c-Myb. We show he re that a leucine-zipper structure is a component of the negative regu latory domain, because its disruption markedly increases both the tran sactivating and transforming capacities of c-Myb. We also demonstrate that this leucine-zipper structure can interact with cellular proteins . Our results suggest that an inhibitor that suppresses transactivatio n binds to c-Myb through the leucine zipper and that c-Myb can be onco genically activated by missense mutation.