Isolation and characterization of a 28-kDa HMG-like protein that binds to A/T-rich distal promoter regions of zein genes

Plant chromosomal non-histone high mobility group (HMG) proteins contribute substantially to the protein/DNA interactions with A/T-rich DNA regions. Here, we demonstrate the existence of a novel maize 28 kDa HMG-like protein which is rich in basic and acidic amino acid residues and which has a high proline content. This HMG-like protein factor was isolated and characterized using 0.35 M NaCl extraction, 2% trichloroacetic acid (TCA) precipitation and ultracentrifugation. As shown by southwestern and band shift experiments, this 28-kDa protein interacts specifically with distal A/T-rich elements in the 5' flanking region of the Zcl zein gene. Competition experiments with distamycin A indicate that the protein binds A/T stretches predominantly through minor groove contacts. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.