A Highly Sensitive Plant Hybrid Protein Assay System Based on the Spm Promoter and TnpA Protein for Detection and Analysis of Transcription Activation Domains
Plant Molecular Biology, Vol. 32, No. 4 (November 1996): 717-725. DOI.
Michael Schläppi was affiliated with the Carnegie Institution of Washington at the time of publication.
TnpA is a multifunctional DNA binding protein encoded by the maize Suppressor-mutator (Spm) transposable element. TnpA is required for transposition and is a repressor of the unmethylated Spm promoter. While analyzing protein domains using a yeast GAL4-based hybrid system in transiently transformed tobacco cells, we found that TnpA represses the >10-fold transcriptional activation observed when the GAL4 DNA-binding domain is used alone. By contrast, compared to the backgroundless TnpA DNA-binding domain alone, 33-to 45-fold activation of the Spm promoter was observed when the VP16 activation domain was fused to it. TnpA-binding sites, but no TATA box, were required for transcription activation. Among the TnpA deletion derivatives tested, those retaining the coding sequences for the DNA-binding and protein dimerization domains gave the highest level of transcription activation when fused with the VP16 activation domain. The TnpA gene and TnpA-binding sites in the short Spm promoter therefore provide a novel, highly sensitive single-hybrid system for identifying and studying plant transcription activation domains in plant cells.