PHYLOGENETIC-RELATIONSHIPS OF HMG BOX DNA-BINDING DOMAINS

HMG boxes were initially identified as DNA-binding domains of the huma n RNA polymerase I (pol I) transcription factor hUBF and the animal hi gh-mobility-group (HMG) protein family HMG1. Since then, numerous sequ ences of HMG-box-containing HMG proteins and other DNA-binding protein s from several species have become available. By sequence comparisons of a selected range of HMG boxes from these proteins and the construct ion of phylogenetic trees we show that the HMG box is highly conserved between DNA-binding proteins of organisms from all three eukaryotic k ingdoms and that HMG boxes are linked by distinct evolutionary relatio nships. In addition, most HMG boxes display comparable hydropathy prof iles and amino acid arrangements, which could serve as nuclear targeti ng sequences.