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Structural Basis of Glucocorticoid Receptor Recognition of Both Unmodified and Methylated Ancient Binding Sites, Precursors for a Modern Recognition Element
Author(s) -
Liu Xu,
Weikum Emily,
Ortlund Eric
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.533.61
Subject(s) - methylation , dna methylation , cpg site , biology , binding site , cytosine , deamination , dna binding site , genetics , glucocorticoid receptor , dna , biochemistry , gene , promoter , enzyme , gene expression
DNA methylation plays crucial roles in gene silencing and development in eukaryotic cells. The most common DNA methylation involves the addition of a methyl group to a cytosine base in the context of a cytosine‐phosphate‐guanine (CpG) dinucleotide. Ancient genomes were enriched in CpG sites that may have served as transcription factor (TF) binding sites. These sites, through the process of methylation, deamination and subsequent mutation to TpG sites, may have maintained equal or enhanced TF binding. Recently, this has been described as a “mutator” system to produce genetic diversity during evolution. Here we test feasibility of this hypothesis by using an ancestral glucocorticoid receptor (GR) binding site (aGBS) that contains a CpG dinucleotide. We examine the binding of GR to ancestral unmodified, methylated and extant GBS and find two‐fold affinity increase upon the methylation and deamination. Additionally, this binding specificity is maintained from ancient steroid receptor AncSR2 to extant GR during the evolution. We also present the first structural studies of GR binding to unmodified and methylated aGBS. A methyl‐specific van der Walls contact with a Arg residue in the GR recognition helix is the molecular determinant of the binding specificity. Our study provides the first biochemical and structural evidence of high affinity binding for ancestral GR binding site containing methylated CpG, which could evolve to the extant, TpG‐containing site. This also indicates GR recognition of methylated CpG‐containing site is ancestral and offers new insight into evolution of steroid receptors and their binding sites. Support or Funding Information These studies were supported by National Institutes of Health [R01DK095750] and W.M. Keck Foundation Medical Research Grant to E. O. X.L was supported by an American Heart Association postdoctoral fellowship [17POST33660110]. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .