THE C-MYB ONCOPROTEIN

The c-myb gene is the cellular homologue of the v-myb oncogenes carrie d by the avian leukaemia viruses AMV and E26. It encodes a transcripti on factor (c-Myb), as does each of the viral oncogenes, which recognis es the core DNA sequence C/T-A-A-C-G/T-G via a repeated helix-turn-hel ix-like motif. c-myb is expressed in immature haemopoietic cells, as w ell as immature cells of the gastro-intestinal epithelium and is down- regulated with differentiation. Enforced expression of activated or ev en normal forms of Myb can transform haemopoietic cells, most often of the myeloid lineage, in vitro and in vivo. Although many genes have b een identified which are likely to be regulated by c-Myb, the critical target genes involved in Myb's transforming activity are not known. T ogether with data showing increased c-myb expression in colonic tumour s, these observations raise the possibility that c-myb may play a role in human malignant disease. (C) 1998 Elsevier Science Ltd. All rights reserved.