HMG1 is an evolutionarily highly conserved chromosomal protein consisting of two folded DNA-binding domains, A and B ("high mobility group (HMG) boxes"), and an acidic C-terminal domain. Several lines of evidence suggest that previously reported sequence-independent DNA bending and looping by HMG1 and its HMG box domains might be important for the proposed role of the protein in transcription and recombination. We have used ligase-mediated circularization assays to investigate the contribution of the individual A and B HMG1 box domains and of the linker region between A/B- and B/C-domains, which flank the "minimal" B-domain (residues 92-162), to the ability of the HMG1 protein (residues 1-215) to bend DNA. Neither the minimal B-domain nor the minimal B-domain with a 7-residue N-terminal extension (85TKKKFKD91) bent the DNA. The attachment of an extra 18-residue C-terminal additional extension (residues 163-180) to the minimal B-domain had only a small effect on the ability of the HMG box to bend DNA. On the other hand, circularization assay with a B-domain having both 7-residue N-terminal and 18-residue C-terminal flanking sequences (residues 85-180) revealed a strong bending of the DNA, suggesting that both extensions are a prerequisite for efficient DNA bending by the B-domain. We have also shown that a single lysine residue (Lys90) in a short N-terminal sequence 90KD91 attached to the B-domain is sufficient for strong distortion of DNA by bending, provided that the B-domain is flanked by the 18-residue C-terminal flanking sequence. Although the DNA bending potential of HMG1 seems to be predominantly due to the B-domain flanked by basic sequences, covalent attachment of the A- and B-domains is necessary for efficient DNA flexure and the ability of the (A+B)-bidomain to bend DNA is further modulated in the native HMG1 protein by its acidic C-domain.

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

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

Binding of histone H1 to DNA is differentially modulated by redox state of HMGB1

HMGB1 gene knockout in mouse embryonic fibroblasts results in reduced telomerase activity and telomere dysfunction

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

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