Molecular Genetics and Epigenetics of CACTA Elements

  • Nina V. Fedoroff
Part of the Methods in Molecular Biology book series (MIMB, volume 1057)


The CACTA transposons, so named for a highly conserved motif at element ends, comprise one of the most abundant superfamilies of Class 2 (cut-and-paste) plant transposons. CACTA transposons characteristically include subterminal sequences of several hundred nucleotides containing closely spaced direct and inverted repeats of a short, conserved sequence of 14-15 bp. The Supressor-mutator (Spm) transposon, identified and subjected to detailed genetic analysis by Barbara McClintock, remains the paradigmatic element of the CACTA family. The Spm transposon encodes two proteins required for transposition, the transposase (TnpD) and a regulatory protein (TnpA) that binds to the subterminal repeats. Spm expression is subject to both genetic and epigenetic regulation. The Spm-encoded TnpA serves as an activator of the epigenetically inactivated, methylated Spm, stimulating both transient and heritable activation of the transposon. TnpA also serves as a negative regulator of the demethylated active element promoter and is required, in addition to the TnpD, for transposition.

Key words

CACTA elements transposon Suppressor-mutator Spm transposition TnpA TnpD epigenetic regulation 


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Copyright information

© Springer Science+Business Media, New York 2013

Authors and Affiliations

  • Nina V. Fedoroff
    • 1
    • 2
  1. 1.Huck Institutes of the Life SciencesPenn State UniversityUniversity ParkUSA
  2. 2.King Abdullah University of Science and Technology (KAUST)ThuwalSaudi Arabia

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