THE PLANT CELL, Vol 8, Issue 9 1569-1587, Copyright © 1996 by American Society of Plant Biologists
Binding of the Wheat Basic Leucine Zipper Protein EmBP-1 to Nucleosomal Binding Sites Is Modulated by Nucleosome Positioning
X. Niu, C. C. Adams, J. L. Workman and M. J. Guiltinan
Department of Horticulture, Biotechnology Institute, Pennsylvania State University, University Park, Pennsylvania 16802
To investigate interactions of the basic leucine zipper transcription
factor EmBP-1 with its recognition sites in nucleosomal DNA, we
reconstituted an abscisic acid response element and a high-affinity binding
site for EmBP-1 into human and wheat nucleosome cores in vitro. DNA binding
studies demonstrated that nucleosomal elements can be bound by EmBP-1 at
reduced affinities relative to naked DNA. EmBP-1 affinity was lowest when
the recognition sites were positioned near the center of the nucleosome.
Binding was achieved with a truncated DNA binding domain; however, binding
of full-length EmBP-1 caused additional strong DNase I hypersensitivity
flanking the binding sites. Similar results were observed with nucleosomes
reconstituted with either human or wheat histones, demonstrating a
conserved mechanism of transcription factor-nucleosome interactions. We
conclude that positioning of recognition sequences on a nucleosome may play
an important role in regulating interactions of EmBP-1 with its target
sites in plant cells.
