Transcription interference-mediated silencing without chromatin changes. (a) Top: a wild-type maternal allele does not express Airn lncRNA as its promoter is repressed by a DNA methylation imprint, thus allowing the Igf2r gene to be active. Middle: on the wild-type paternal allele Airn transcription overlaps with and silences the Igf2r pc gene promoter, independent of the Airn lncRNA product. The silent Igf2r promoter is marked by increased nucleosome density and DNA methylation in the absence of active histone modifications. Bottom: increased nucleosome density, loss of active histone marks and DNA methylation are not necessary for Igf2r repression as demonstrated by the FAP allele that moved the Airn promoter close to the Igf2r promoter and silenced Igf2r in the absence of repressive chromatin features. (b) Top: a hypothetical enhancer activates a pc gene by direct long-range DNA interactions. Bottom: transcription of a lncRNA overlapping the enhancer interferes with the DNA interaction and thereby silences the pc gene. For details see Figure 1g, Figure 2d and text.
Kornienko et al. BMC Biology 2013 11:59 doi:10.1186/1741-7007-11-59