| First Author | Stros M | Year | 2000 |
| Journal | J Biol Chem | Volume | 275 |
| Issue | 46 | Pages | 35699-707 |
| PubMed ID | 10962007 | Mgi Jnum | J:65778 |
| Mgi Id | MGI:1927289 | Doi | 10.1074/jbc.M007167200 |
| Citation | Stros M, et al. (2000) A role of basic residues and the putative intercalating phenylalanine of the HMG-1 box B in DNA supercoiling and binding to four-way DNA junctions. J Biol Chem 275(46):35699-707 |
| abstractText | HMG (high mobility group) 1 is a chromosomal protein with two homologous DNA-binding domains, the HMG boxes A and B. HMG-1, like its individual HMG boxes, can recognize structural distortion of DNA, such as four-way DNA junctions (4WJs), that are very likely to have features common to their natural, yet unknown, cellular binding targets. HMG-1 can also bend/loop DNA and introduce negative supercoils in the presence of topoisomerase I in topologically closed DNAs. Results of our gel shift assays demonstrate that mutation of Arg(97) within the extended N-terminal strand of the B domain significantly (>50-fold) decreases affinity of the HMG box for 4WJs and alters the mode of binding without changing the structural specificity for 4WJs. Several basic amino acids of the extended N-terminal strand (Lys(96)/Arg(97)) and helix I (Arg(110)/Lys(114)) of the B domain participate in DNA binding and supercoiling. The putative intercalating hydrophobic Phe(103) of helix I is important for DNA supercoiling but dispensable for binding to supercoiled DNA and 4WJs. We conclude that the B domain of HMG-1 can tolerate substitutions of a number of amino acid residues without abolishing the structure-specific recognition of 4WJs, whereas mutations of most of these residues severely impair the topoisomerase I-mediated DNA supercoiling and change the sign of supercoiling from negative to positive. |
