The suppressor-mutator element and the evolutionary riddle of transposons.
This review focuses on the epigenetic control of the maize Suppressor-mutator (Spm) transposon and the evolutionary origin of epigenetic mechanisms. Methylation of the Spm promoter prevents transcription and transposition, and the methylation of the adjacent GC-rich sequence renders the inactive state heritable. Spm encodes an epigenetic activator, TnpA, one of the two Spm-encoded transposition proteins. TnpA can reactivate an inactive, methylated Spm both transiently and heritably, and it is also a transcriptional repressor of the unmethylated Spm promoter. Features common to epigenetic mechanisms in general suggest that they originated as a means of decreasing the recombinogenicity of duplicated sequences.
Fedoroff
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NV
Biology Department and Biotechnology Institute, The Pennsylvania State University, University Park, PA 16802, USA. nvf1@psu.edu
D004251:DNA Transposable Elements / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D019143:Evolution, Molecular; D020440:Gene Duplication; D005786:Gene Expression Regulation; D008745:Methylation; D008957:Models, Genetic; D010940:Plant Proteins; D030821:Plants, Genetically Modified; D012097:Repressor Proteins / Q000235:genetics; D013489:Suppression, Genetic / Q000235:genetics*
D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D010940:Plant Proteins; D012097:Repressor Proteins