Nucleic Acids Research, Vol 22, Issue 23 4969-4978, Copyright © 1994 by Oxford University Press

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ARTICLES

DNA binding specificity of the wheat bZIP protein EmBP-1

X Niu and MJ Guiltinan

Department of Horticulture, Pennsylvania State University, University Park 16802.

EmBP-1 is a wheat DNA binding protein of the basic leucine zipper (bZIP) class of transcription factors implicated in the mechanisms of abscisic acid mediated gene activation. Understanding the role of EmBP- 1 in regulating gene transcription requires elucidation of its DNA binding specificity. The binding of EmBP-1 was studied using gel shift selection of DNA from random sequence pools. DNA binding sites were identified by sequencing of a selected pool and by cloning and sequencing individual sites. The binding sites were compared by mobility shift assay and DNase I footprinting, which show that EmBP-1 binds to a family of sequences with varying degrees of affinity. The highest affinity site bound by EmBP-1 is the palindrome GCCACGTGGC. EmBP-1 also binds several other sequences with high affinity, however most of these are asymmetric. While nearly all sequences bound by EmBP- 1 contain an ACGT core sequence, EmBP-1 can also bind at least two sites with altered cores. These results provide a basis for comparing the DNA binding specificity of EmBP-1 with those of other plant bZIP proteins and provide insight into the possible target sites which EmBP- 1 might bind in vivo.