Epigenetic regulation of the maize Spm transposable element: Novel activation of a methylated promoter by TnpA

Michael Schläppi, Ramesh Raina, Nina Fedoroff

Research output: Contribution to journalArticle

70 Scopus citations


Spm is epigenetically inactivated by C-methylation near its transcription start site. We have investigated the interaction between TnpA, an autoregulatory protein that can reactivate a silent Spm, and the promoter of the element. The promoter undergoes rapid de novo methylation and inactivation in stably transformed plants, but only if it includes a GC-rich sequence downstream of the promoter. TnpA activates the inactive, methylated promoter and leads to reduced methylation. By contrast, TnpA represses the active, unmethylated Spm promoter. Only the internal DNA-binding and dimerization domains of the protein are required for repression, while activation requires an additional C-terminal sequence. TnpA is therefore a unique regulatory protein with a conventional transcriptional repressor activity and a novel ability to activate a methylated, inactive promoter.

Original languageEnglish (US)
Pages (from-to)427-437
Number of pages11
Issue number3
StatePublished - May 6 1994
Externally publishedYes


ASJC Scopus subject areas

  • Cell Biology
  • Molecular Biology

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