Spacing between GT-1 binding sites within a light-responsive element is critical for transcriptional activity.
Dissection of the light-responsive element (LRE) located between -166 and -50 of rbcS-3A from pea has revealed critical spacing requirements between the two GT-1 binding sites for light-responsive transcription. An increase in spacing between the two sites by as little as 2 bp reduces dramatically the rbcS-3A transcript levels in vivo. Mutation of the 10 bp between the binding sites leads to slightly lower transcript levels, as do deletions of either 3 bp or 8 bp. Deletions of 5 bp or 7 bp from between the GT-1 binding sites do not affect rbcS-3A transcript levels; however, a deletion of 10 bp virtually abolishes the activity of this element. These spacing changes within the light-responsive element similarly affect transcription of a divergently oriented and truncated nopaline synthase promoter. Most spacing changes between the two GT-1 binding sites, however, do not impair the binding of GT-1 to this element in vitro. Together with previous observations, these results suggest that the nuclear factor GT-1 may interact with the binding sites in either a productive or nonproductive manner and that GT-1 binding is necessary but not sufficient for light-responsive transcription. We also discuss our results in relation to the observed spacing of similar sequence elements present within other light-responsive promoters.
Gilmartin
P M
PM
Laboratory of Plant Molecular Biology, Rockefeller University, New York, New York 10021-6399.
Chua
N H
NH
D000594:Amino Acid Oxidoreductases / Q000235:genetics; D001483:Base Sequence; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000378:metabolism*; D007887:Fabaceae / Q000235:genetics*; D017343:Genes, Plant / Q000235:genetics*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D010775:Photic Stimulation; D030821:Plants, Genetically Modified / Q000235:genetics; D010946:Plants, Medicinal; D010947:Plants, Toxic; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics*; D014026:Nicotiana / Q000235:genetics; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000528:radiation effects*
D004268:DNA-Binding Proteins; C077926:GT-1 transcription factor; D009687:Nuclear Proteins; D014157:Transcription Factors; D000594:Amino Acid Oxidoreductases; C021883:nopaline synthase; D012273:Ribulose-Bisphosphate Carboxylase