Enhancement of DNA flexibility in vitro and in vivo by HMGB box A proteins carrying box B residues

Nadia T. Sebastian, Emily M. Bystry, Nicole A. Becker, L. James Maher

Research output: Contribution to journalArticle

16 Scopus citations


HMGB proteins are abundant non-histone components of eukaryotic chromatin. The biological function of DNA sequence-nonspecific HMGB proteins is obscure. These proteins are composed of one or two conserved HMG box domains, each forming three R-helices that fold into a sequence-nonspecific DNA-binding module recognizing the DNA minor groove. Box A and box B homology domains have subtle sequence differences such that box B domains bend DNA strongly while DNA bending by isolated box A domains is weaker. Both box A and box B domains preferentially bind to distorted DNA structures. Here we show using DNA cyclization kinetics assays in vitro and Escherichia coli DNA looping assays in vivo that an isolated HMG box A domain derived from human HMGB2 folds poorly and does not enhance apparent DNA flexibility. Surprisingly, substitution of a small number of cationic residues from the N-terminal leader of a functional yeast box B protein, Nhp6Ap, confers the ability to enhance DNA flexibility. These results demonstrate important roles for cationic leader amino acids in HMGB folding, DNA interaction, and DNA bending.

Original languageEnglish (US)
Pages (from-to)2125-2134
Number of pages10
Issue number10
StatePublished - Mar 17 2009

ASJC Scopus subject areas

  • Biochemistry

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