MYB DNA-BINDING INHIBITED BY PHOSPHORYLATION AT A SITE DELETED DURING ONCOGENIC ACTIVATION

The c-Myb nuclear oncoprotein is phosphorylated in vitro and in vivo at an N-terminal site near its DNA-binding domain by casein kinase II (CK-II) or a CK-ll-like activity. This in vitro phosphorylation reversibly inhibits the sequence-specific binding of c-Myb to DNA. The site of this phosphorylation is deleted in nearly all oncogenically activated Myb proteins, resulting in DNA-binding that is indepen-dent of CK-II. Because CK-II activity is modulated by growth factors, loss of the site could uncouple c-Myb from its normal physiological regulator. © 1990 Nature Publishing Group.