title: A conserved Myc protein domain, MBIV, regulates DNA binding, apoptosis, transformation, and G2 arrest.
abstract: The myc family of oncogenes is well conserved throughout evolution. Here we present the characterization of a domain conserved in c-, N-, and L-Myc from fish to humans, N-Myc317-337, designated Myc box IV (MBIV). A deletion of this domain leads to a defect in Myc-induced apoptosis and in some transformation assays but not in cell proliferation. Unlike other Myc mutants, MycDeltaMBIV is not a simple loss-of-function mutant because it is hyperactive for G2 arrest in primary cells. Microarray analysis of genes regulated by N-MycDeltaMBIV reveals that it is weakened for transactivation and repression but not nearly as defective as N-MycDeltaMBII. Although the mutated region is not part of the previously defined DNA binding domain, we find that N-MycDeltaMBIV has a significantly lower affinity for DNA than the wild-type protein in vitro. Furthermore, chromatin immunoprecipitation shows reduced binding of N-MycDeltaMBIV to some target genes in vivo, which correlates with the defect in transactivation. Thus, this conserved domain has an unexpected role in Myc DNA binding activity. These data also provide a novel separation of Myc functions linked to the modulation of DNA binding activity.
authors.affiliation: Department of Pharmacology, Norris Cotton Cancer Center, Dartmouth Medical School, One Medical Center Drive, Lebanon, NH 03756, USA.
authors.forename: Victoria H
authors.initials: VH
authors.lastname: Cowling
authors.forename: Sanjay
authors.initials: S
authors.lastname: Chandriani
authors.forename: Michael L
authors.initials: ML
authors.lastname: Whitfield
authors.forename: Michael D
authors.initials: MD
authors.lastname: Cole
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D017124:Conserved Sequence / Q000235:genetics*; D004247:DNA / Q000378:metabolism*; D015536:Down-Regulation / Q000235:genetics; D005347:Fibroblasts / Q000166:cytology; D016195:G2 Phase / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D046228:Microarray Analysis; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D016271:Proto-Oncogene Proteins c-myc / Q000737:chemistry* / Q000378:metabolism*; D051381:Rats; D017384:Sequence Deletion / Q000235:genetics; D015533:Transcriptional Activation / Q000235:genetics
chemical_list: D016271:Proto-Oncogene Proteins c-myc; D004247:DNA