Research Article

Plant Molecular Biology

, Volume 32, Issue 4, pp 717-725

First online:

A highly sensitive plant hybrid protein assay system based on the Spm promoter and TnpA protein for detection and analysis of transcription activation domains

  • Michael SchläppiAffiliated withDepartment of Embryology, Carnegie Institution of Washington
  • , Ramesh RainaAffiliated withDepartment of Embryology, Carnegie Institution of Washington
  • , Nina FedoroffAffiliated withDepartment of Embryology, Carnegie Institution of Washington

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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.

Key words

hybrid protein plant assay Spm TnpA transcription activation transposon