High mobility group (HMG) 1 protein and its two homologous DNA-binding domains, A and B ("HMG-boxes"), can bend and supercoil DNA in the presence of topoisomerase I, as well as recognize differently bent and distorted DNA structures, including four-way DNA junctions, supercoiled DNA and DNA modified with anticancer drug cisplatin. Here we show that the lysine-rich part of the linker region between A and B domains of HMG-1, the (85)TKKKFKD(91) sequence that is attached to the N-terminus of the B domain within HMG-1, is a prerequisite for a preferential binding of the B domain to supercoiled DNA. The above sequence is also essential for a high-affinity binding of the B domain to DNA containing a site-specific major 1,2-d(GpG) intrastrand DNA adduct of cisplatin. Mutation of Arg(97), but not Lys(90) [Lys(90) forms a specific cross-link with platinum(II) in major groove of cisplatin-modified DNA; Kane, S. A., and Lippard, S. J. (1996) Biochemistry 35, 2180--2188], to alanine significantly (>40-fold) reduces affinity of the B domain to cisplatin-modified DNA, inhibits the ability of the B domain to bend (ligase-mediated circularization) or supercoil DNA, and results in a loss of the preferential binding of the B domain to supercoiled DNA without affecting the structural-specificity of the HMG-box for four-way DNA junctions. Some of the reported activities of the B domain are enhanced when the B domain is covalently linked to the A domain. We propose that binding of the A/B linker region within the major DNA groove helps the two HMG-1 domains to anchor to the minor DNA groove to facilitate their DNA binding and other activities.

Institute of Biophysics Academy of Sciences of the Czech Republic Královopolská 135 612 65 Brno Czech Republic

References provided by Crossref.org

Histone H1 Differentially Inhibits DNA Bending by Reduced and Oxidized HMGB1 Protein

Replacement of a thiourea with an amidine group in a monofunctional platinum-acridine antitumor agent. Effect on DNA interactions, DNA adduct recognition and repair

HMGB1 and HMGB2 proteins up-regulate cellular expression of human topoisomerase IIalpha

Conformation of DNA GG intrastrand cross-link of antitumor oxaliplatin and its enantiomeric analog

HMGB1 interacts with human topoisomerase IIalpha and stimulates its catalytic activity

Chiral differentiation of DNA adducts formed by enantiomeric analogues of antitumor cisplatin is sequence-dependent

DNA-protein cross-linking by trans-[PtCl(2)(E-iminoether)(2)]. A concept for activation of the trans geometry in platinum antitumor complexes