Abstract
In order to study the role played by cellular RNA pools produced by homologous genomic loci in defining the transcriptional state of a silenced gene, we tested the effect of non-functional alleles of the white gene in the presence of a functional copy of white, silenced by heterochromatin. We found that non-functional alleles of white, unable to produce a coding transcript, could reactivate in trans the expression of a wild type copy of the same gene silenced by heterochromatin. This new epigenetic phenomenon of transcriptional trans-reactivation is heritable, relies on the presence of homologous RNA’s and is affected by mutations in genes involved in post-transcriptional gene silencing. Our data suggest a general new unexpected level of gene expression control mediated by homologous RNA molecules in the context of heterochromatic genes.
Highlights
In recent years it has become increasingly evident that the expression of eukaryotic genomes is far more complex than it had been previously explored
We discovered a new epigenetic phenomenon we called trans-reactivation
Unable to produce a functional coding transcript, but with the potential of transcribing other RNA’s within their gene body, strongly reactivate the transcription of a wildtype copy of the same gene silenced by heterochomatin. This new epigenetic phenomenon is heritable, relies on the presence of diffusible RNAs able to carry and transfer epigenetic information and is affected by mutations in genes involved in Post-Transcriptional Gene Silencing
Summary
In recent years it has become increasingly evident that the expression of eukaryotic genomes is far more complex than it had been previously explored. The unusual epigenetic phenomena of paramutation [13,14,15], trans-induction [16] and transvection [17,18] observed in a variety of higher eukaryotes involve the activity of ncRNAs that ‘rewrite’ the transcriptional state of an allele, in processes that apparently escape classic Mendel’s laws of genetic inheritance. These epigenetic phenomena are clear examples of ncRNAdirected regulatory processes that transfer epigenetic information both across cells, between tissues and across generations, though the mechanisms underlying these phenomena still remain elusive
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