Epigenetic regulation of the maize Spm transposable element: novel activation of a methylated promoter by TnpA.
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 down-stream 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.
Schläppi
M
M
Carnegie Institution of Washington, Department of Embryology, Baltimore, Maryland 21210.
Raina
R
R
Fedoroff
N
N
D001483:Base Sequence; D004247:DNA / Q000378:metabolism; D004251:DNA Transposable Elements / Q000235:genetics*; D004268:DNA-Binding Proteins; D017343:Genes, Plant / Q000235:genetics*; D008745:Methylation; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000166:cytology / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D011487:Protein Conformation; D012097:Repressor Proteins; D017384:Sequence Deletion / Q000235:genetics; D014158:Transcription, Genetic; D015533:Transcriptional Activation / Q000235:genetics*; D003313:Zea mays / Q000235:genetics
D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D010940:Plant Proteins; D012097:Repressor Proteins; D004247:DNA