A tobacco DNA binding protein that interacts with a light-responsive box II element.
Ribulose-1,5-bisphosphate carboxylase/oxygenase plays a key role in photosynthetic carbon fixation in higher plants. The small subunit of this chloroplast enzyme (rbcS), encoded by a family of nuclear genes, is regulated at the transcriptional level by light. Promoter analyses have previously identified the box II sequence as a cis element critical for the light-regulated expression of rbcS genes. Nuclear factor GT-1 binds specifically to this element and is one of the plant nuclear factors that has been detected and studied in great detail. Here we describe the cloning and characterization of a tobacco cDNA encoding a protein, designated B2F (Box II Factor), with similar binding specificity and mobility in gel retardation assays as nuclear GT-1. Steady state levels of mRNA encoding B2F do not appear to be regulated by light; this is consistent with the previous observation that nuclear GT-1 activity is present in extracts from both light-grown and dark-adapted plants. Sequence comparison with another plant trans-acting factor, GT-2, which binds to a GT-like element in the rice phytochrome promoter, shows striking homology in three putative alpha-helices that may be involved in DNA binding.
Perisic
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AgBiotech Center, Waksman Institute, Rutgers State University, Piscataway, New Jersey 08855.
Lam
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D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D008027:Light; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D010947:Plants, Toxic; D012045:Regulatory Sequences, Nucleic Acid; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics*; D014158:Transcription, Genetic / Q000528:radiation effects
D004268:DNA-Binding Proteins; D010940:Plant Proteins; C077483:B2F protein, Nicotiana tabacum; D004247:DNA