Epigenetic regulation of the maizeSpmtransposon

Expression and transposition of the Suppressor-mutator transposon of maize are controlled by interacting epigenetic and autoregulatory mechanisms.

Nina Fedoroff; Michael Schläppi; Ramesh Raina

2005

Scholarcy highlights

  • Expression and transposition of the Suppressor-mutator transposon of maize are controlled by interacting epigenetic and autoregulatory mechanisms.
  • Methylation of critical element sequences prevents both transcription and transposition, heritably inactivating the element.
  • The promoter, comprising the terminal 0.2 kb of the element, and a 0.35-kb, highly GC-rich, downstream sequence are the methylation target sequences.
  • The element encodes two proteins necessary for transposition, TnpA and TnpD.
  • There are multiple TnpA binding sites, both in the 5′ terminal promoter region and at the element's 3′ end.
  • In addition to its role in transposition, TnpA is both a positive and a negative regulator of transcription.
  • TnpA represses the element's promoter when it is not methylated.
  • When the element is inactive and its promoter methylated, TnpA activates the methylated promoter and facilitates both its transient and heritable demethylation.

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