Plant chromosomal HMGI/Y proteins and histone H1 exhibit a protein domain of common origin

The chromosomal high-mobility-group (HMG) proteins of the HMGI/Y family int eract with A/T-rich stretches in duplex DNA, and are considered assistant f actors in transcriptional regulation. A cDNA encoding an HMGI/Y protein of 190 amino acid residues was isolated from maize and characterized. Like oth er plant HMGI/Y proteins, the maize HMGI/Y protein contains four copies of the AT-hook DNA-binding motif and an amino-terminal 'histone H1-like region ' with a similarity to the globular domain of H1. The maize hmgi/y gene tha t was isolated from a genomic DNA library contains a single intron that is localized in the region of sequence similarity to histone H1. Interestingly , the genes encoding plant H1 contain an intron at exactly the same relativ e position, indicating an evolutionary relationship of the plant genes enco ding HMGI/Y and H1 proteins. (C) 1999 Elsevier Science B.V. All rights rese rved.