title: Transcriptional enhancement by GATA1-occupied DNA segments is strongly associated with evolutionary constraint on the binding site motif.
abstract: Tissue development and function are exquisitely dependent on proper regulation of gene expression, but it remains controversial whether the genomic signals controlling this process are subject to strong selective constraint. While some studies show that highly constrained noncoding regions act to enhance transcription, other studies show that DNA segments with biochemical signatures of regulatory regions, such as occupancy by a transcription factor, are seemingly unconstrained across mammalian evolution. To test the possible correlation of selective constraint with enhancer activity, we used chromatin immunoprecipitation as an approach unbiased by either evolutionary constraint or prior knowledge of regulatory activity to identify DNA segments within a 66-Mb region of mouse chromosome 7 that are occupied by the erythroid transcription factor GATA1. DNA segments bound by GATA1 were identified by hybridization to high-density tiling arrays, validated by quantitative PCR, and tested for gene regulatory activity in erythroid cells. Whereas almost all of the occupied segments contain canonical WGATAR binding site motifs for GATA1, in only 45% of the cases is the motif deeply preserved (found at the orthologous position in placental mammals or more distant species). However, GATA1-bound segments with high enhancer activity tend to be the ones with an evolutionarily preserved WGATAR motif, and this relationship was confirmed by a loss-of-function assay. Thus, GATA1 binding sites that regulate gene expression during erythroid maturation are under strong selective constraint, while nonconstrained binding may have only a limited or indirect role in regulation.
authors.affiliation: Center for Comparative Genomics and Bioinformatics of the Huck Institutes of Life Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Cheng
authors.forename: David C
authors.initials: DC
authors.lastname: King
authors.forename: Louis C
authors.initials: LC
authors.lastname: Dore
authors.forename: Xinmin
authors.initials: X
authors.lastname: Zhang
authors.forename: Yuepin
authors.initials: Y
authors.lastname: Zhou
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Christine
authors.initials: C
authors.lastname: Dorman
authors.forename: Demesew
authors.initials: D
authors.lastname: Abebe
authors.forename: Swathi A
authors.initials: SA
authors.lastname: Kumar
authors.forename: Francesca
authors.initials: F
authors.lastname: Chiaromonte
authors.forename: Webb
authors.initials: W
authors.lastname: Miller
authors.forename: Roland D
authors.initials: RD
authors.lastname: Green
authors.forename: Mitchell J
authors.initials: MJ
authors.lastname: Weiss
authors.forename: Ross C
authors.initials: RC
authors.lastname: Hardison
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D033481:Chromosomes, Mammalian; D004247:DNA / Q000235:genetics*; D004742:Enhancer Elements, Genetic; D019143:Evolution, Molecular; D050982:GATA1 Transcription Factor / Q000737:chemistry* / Q000235:genetics*; D005786:Gene Expression Regulation; D051379:Mice; D010802:Phylogeny; D015203:Reproducibility of Results; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
chemical_list: D050982:GATA1 Transcription Factor; C494689:Gata1 protein, mouse; D004247:DNA