title: Positive and negative determinants of target gene specificity in myb transcription factors.
abstract: The A-Myb and c-Myb transcription factors share a highly conserved DNA-binding domain and activate the same promoters in reporter gene assays. However, the two proteins have distinct biological activities, and expressing them individually in human cells leads to the activation of distinct sets of endogenous genes, suggesting that each protein has a unique transcriptional specificity. Here, the structural and functional features of the Myb proteins were compared, using assays of endogenous gene expression to measure changes in specificity. When the Myb proteins were tested in different cell types, they activated unique and nearly nonoverlapping sets of genes in each cellular context. Deletion and domain swap experiments identified small, discreet positive and negative elements in A-Myb and c-Myb that were required for the regulation of specific genes, such as DHRS2, DSIPI, and mim-1. The results suggest that individual functional elements in the transcriptional activation domains are responsible for activating specific cellular genes in a context-specific manner. The results also have important implications for interpreting results from reporter gene assays, which fail to detect the differences in activity identified through endogenous gene assays, and fusion protein constructs that alter the transcriptional activation domains and the activities of the Myb proteins.
authors.affiliation: Department of Molecular Genetics and Microbiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131-0001, USA.
authors.forename: Wanli
authors.initials: W
authors.lastname: Lei
authors.forename: John J
authors.initials: JJ
authors.lastname: Rushton
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Davis
authors.forename: Fan
authors.initials: F
authors.lastname: Liu
authors.forename: Scott A
authors.initials: SA
authors.lastname: Ness
mesh_terms: D000818:Animals; D002645:Chickens; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D017434:Protein Structure, Tertiary; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D020598:Proto-Oncogene Proteins c-myb; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors