title: Mechanism of high-mobility group protein B enhancement of progesterone receptor sequence-specific DNA binding.
abstract: The DNA-binding domain (DBD) of progesterone receptor (PR) is bipartite containing a zinc module core that interacts with progesterone response elements (PRE), and a short flexible carboxyl terminal extension (CTE) that interacts with the minor groove flanking the PRE. The chromosomal high-mobility group B proteins (HMGB), defined as DNA architectural proteins capable of bending DNA, also function as auxiliary factors that increase the DNA-binding affinity of PR and other steroid receptors by mechanisms that are not well defined. Here we show that the CTE of PR contains a specific binding site for HMGB that is required for stimulation of PR-PRE binding, whereas the DNA architectural properties of HMGB are dispensable. Specific PRE DNA inhibited HMGB binding to the CTE, indicating that DNA and HMGB-CTE interactions are mutually exclusive. Exogenous CTE peptide increased PR-binding affinity for PRE as did deletion of the CTE. In a PR-binding site selection assay, A/T sequences flanking the PRE were enriched by HMGB, indicating that PR DNA-binding specificity is also altered by HMGB. We conclude that a transient HMGB-CTE interaction alters a repressive conformation of the flexible CTE enabling it to bind to preferred sequences flanking the PRE.
authors.affiliation: Program in Molecular Biology, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA.
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Roemer
authors.forename: James
authors.initials: J
authors.lastname: Adelman
authors.forename: Mair E A
authors.initials: ME
authors.lastname: Churchill
authors.forename: Dean P
authors.initials: DP
authors.lastname: Edwards
mesh_terms: D000225:Adenine / Q000032:analysis; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D019556:COS Cells; D002522:Chlorocebus aethiops; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D024002:HMGB Proteins / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology; D011485:Protein Binding; D011980:Receptors, Progesterone / Q000737:chemistry* / Q000378:metabolism*; D020218:Response Elements; D013941:Thymine / Q000032:analysis
chemical_list: D024002:HMGB Proteins; D010455:Peptides; D011980:Receptors, Progesterone; D004247:DNA; D000225:Adenine; D013941:Thymine