Photoregulated gene expression may involve ubiquitous DNA binding proteins.
Several promoter elements have previously been shown to influence the expression of the cab-E gene in Nicotiana plumbaginifolia. Here we demonstrate, by electrophoretic mobility shift and methylation interference assays, that a complex pattern of protein-DNA interactions characterizes this promoter. Among the multiple proteins identified, we focused on five different factors which either occupied important regulatory elements and/or were present in relatively large amounts in nuclear extracts. All of these proteins were distinguished on the basis of their recognition sequence and other biochemical parameters. One, GBF, interacted with a single sequence within the cab-E promoter homologous to the G-box found in many photoregulated and other plant promoters. A second factor, GA-1, bound to the GATA element which is located between the CAAT and TATA boxes of the cab-E and all other LHCII Type I CAB promoters. GA-1 also interacted in vitro with the I-boxes of the Arabidopsis rbcS-1A promoter and the as-2 site of the CaMV 35S promoter. Two other factors, GC-1 and AT-1, bound to multiple recognition sites localized within the GC-rich and AT-rich elements, respectively. GT-1, a protein which interacts with promoters of other light-regulated genes, bound to seven distinct sites distributed throughout the cab-E promoter.
Schindler
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Department of Biology, University of Pennsylvania, Philadelphia 19104.
Cashmore
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D001483:Base Sequence; D002734:Chlorophyll / Q000378:metabolism; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation; D008027:Light; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics*; D010947:Plants, Toxic; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D014026:Nicotiana / Q000235:genetics*; D014157:Transcription Factors / Q000502:physiology*
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010940:Plant Proteins; D014157:Transcription Factors; D002734:Chlorophyll