High mobility group protein 1: A collaborator in nucleosome dynamics and estrogen-responsive gene expression.

High mobility group protein 1 (HMGB1) is a multifunctional protein that interacts with DNA and chromatin to influence the regulation of transcription, DNA replication and repair and recombination. We show that HMGB1 alters the structure and stability of the canonical nucleosome (N) in a nonenzymatic, adenosine triphosphate-independent manner. As a result, the canonical nucleosome is converted to two stable, physically distinct nucleosome conformers.

Nucleosome dynamics: HMGB1 relaxes canonical nucleosome structure to facilitate estrogen receptor binding.

High mobility group protein 1 (HMGB1) interacts with DNA and chromatin to influence the regulation of transcription, DNA repair and recombination. We show that HMGB1 alters the structure and stability of the canonical nucleosome (N) in a nonenzymatic, ATP-independent manner. Although estrogen receptor (ER) does not bind to its consensus estrogen response element within a nucleosome, HMGB1 restructures the nucleosome to facilitate strong ER binding.

High mobility group B proteins facilitate strong estrogen receptor binding to classical and half-site estrogen response elements and relax binding selectivity.

The estrogen receptor alpha (ER) is a ligand-dependent transcription factor that regulates the expression of estrogen-responsive genes. A key step in the activation process is the initial binding of the ER dimer to the estrogen response element (ERE). We examined the effect of the coactivator proteins, HMGB1 and HMGB2, in enhancing ER binding affinity to single and tandem EREs.