DNA-binding properties of the recombinant high-mobility-group-like AT-hook-containing region from human BRG1 protein

The hBRG1 protein, a central ATPase of the human switching/sucrose non-fermenting (SWI/SNF) remodeling complex, has a catalytic ATPase domain, an AT-hook motif and a bromodomain. Bromodomains, found in many chromatin-associated proteins, recognize N-acetyl-lysine in histones and other proteins. The AT-hook motif, first described in the high-mobility group of non-histone chromosomal proteins HMGA1/2, is a DNA-binding motif. The AT-hook binds to the AT-rich DNA sequences in the minor groove of B-DNA in a non-sequence specific manner. AT-hook motifs have been identified in many other DNA-binding proteins. In this study we cloned and purified a fragment of hBRG1 encompassing the AT-hook region and the bromodomain. Nuclear magnetic resonance (NMR) and circular dichroism (CD) analyses show that the recombinant domains are structured. The functionality of subdomains was checked by assessing their interactions with N-acetylated peptides from histones and with DNA. Isothermal titration calorimetric (ITC) analysis demonstrates that the primary micromolar interaction is through the AT-hook motif. The AT-hook region binds to linear DNA by unwinding it. These properties resemble the characteristics of the HMGA1/2 proteins and their interaction with DNA.