A conserved acidic patch in the Myb domain is required for activation of an endogenous target gene and for chromatin binding.
The c-Myb protein is a transcriptional regulator initially identified by homology to the v-Myb oncoprotein, and has since been implicated in human cancer. The most highly conserved portion of the c-Myb protein is the DNA-binding domain which consists of three imperfect repeats. Many other proteins contain one or more Myb-related domains, including a number of proteins that do not bind directly to DNA. We performed a phylogenetic analysis of diverse classes of Myb-related domains and discovered a highly conserved patch of acidic residues common to all Myb-related domains. These acidic residues are positioned in the first of three alpha-helices within each of the three repeats that comprise the c-Myb DNA-binding domain. Interestingly, these conserved acidic residues are present on a surface of the protein which is distinct from that which binds to DNA. Alanine mutagenesis revealed that the acidic patch of the third c-Myb repeat is essential for transcriptional activity, but neither for nuclear localization nor DNA-binding. Instead, these acidic residues are required for efficient chromatin binding and interaction with the histone H4 N-terminal tail.
Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5324, USA. emilyeray@gmail.com
Emily Ray
ER
Ko
Dennis
D
Ko
Carolyn
C
Chen
Joseph S
JS
Lipsick
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism*; D017124:Conserved Sequence; D004247:DNA / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D020626:Oncogene Proteins v-myb / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D015533:Transcriptional Activation
D002843:Chromatin; D020626:Oncogene Proteins v-myb; D004247:DNA