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United States Department of Agriculture

Agricultural Research Service

Title: The Hmg-1/y Protein Pf1 Stimulates Binding of the Transcriptional Activatorgt-2 to the Phya Gene Promoter

Authors
item Quail, Peter - UCB-PGEC
item Martinez-Garcia, J. - UCB-PGEC

Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 1, 1999
Publication Date: April 1, 1999
Citation: Quail, P.H., Martinez-Garcia, J.F. 1999. The HMG-I-Y protein PF1 stimulates binding of the transcriptional activator GT-2 to the PHYA gene promoter. Plant Journal 18(2):173-183.

Interpretive Summary: The data suggest the possibility that PF1 may act as an architectural factor, promiscuously recognizing a spectrum of AT-containing elements in plant promoters, with the general function of catalyzing enhanced binding of conventional cognate transcriptional regulators to these elements via DNA bending.

Technical Abstract: The DNA-binding proteins PF1 and GT-2 are factors that bind to different functionally defined, positively acting cis-elements in the PHYA genes of oat and rice, respectively. PF1 is an HMG-I/Y protein, with its cognate cis-element being an AT-rich sequence, designated PE1, whereas GT-2 is a transcriptional activator with twin DNA binding domains that recognize a triplet of GT-boxes in a complex motif designated GTE. To further define the DNA-binding activity of PF1 and to explore potential inter-relationships between the two factors, we have performed a series of in vitro DNA-binding experiments with both PE1 and GTE target sites. The data show that, consistent with its membership of the HMG-I/Y protein family, PF1 can bend DNA when bound to PE1. In addition, PF1 can bind promiscuously, with varying affinity, to other AT-containing motifs, including GTE. When co-incubated with GT-2, PF1 enhances the specific DNA-binding activity of GT-2 toward GTE, the first report of such activity for a plant HMG-I/Y protein. This enhancement takes place without demonstrable physical contact between the two proteins, suggesting the possibility of a novel, indirect mechanism of recruitment involving DNA target-site pre-conditioning. The evidence indicates therefore that PF1 and GT-2 do not perform functionally equivalent roles in positively regulating oat and rice PHYA gene expression. However, the data suggest the possibility that PF1 may act as an architectural factor, promiscuously recognizing a spectrum of AT-containing elements in plant promoters, with the general function of catalyzing enhanced binding of conventional cognate transcriptional regulators to these elements via DNA bending.

Last Modified: 10/21/2014
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