lncRNA PAPAS tethered to the rDNA enhancer recruits hypophosphorylated CHD4/NuRD to repress rRNA synthesis at elevated temperatures.

Attenuation of pre-rRNA synthesis in response to elevated temperature is accompanied by increased levels of PAPAS ("promoter and pre-rRNA antisense") a long noncoding RNA (lncRNA) that is transcribed in an orientation antisense to pre-rRNA. Here we show that PAPAS interacts directly with DNA, forming a DNA-RNA triplex structure that tethers PAPAS to a stretch of purines within the enhancer region, thereby guiding associated CHD4/NuRD (nucleosome remodeling and deacetylation) to the rDNA promoter. Protein-RNA interaction experiments combined with RNA secondary structure mapping revealed that the N-terminal part of CHD4 interacts with an unstructured A-rich region in PAPAS.

Mutations in Cytosine-5 tRNA Methyltransferases Impact Mobile Element Expression and Genome Stability at Specific DNA Repeats.

The maintenance of eukaryotic genome stability is ensured by the interplay of transcriptional as well as post-transcriptional mechanisms that control recombination of repeat regions and the expression and mobility of transposable elements. We report here that mutations in two (cytosine-5) RNA methyltransferases, Dnmt2 and NSun2, impact the accumulation of mobile element-derived sequences and DNA repeat integrity in Drosophila. Loss of Dnmt2 function caused moderate effects under standard conditions, while heat shock exacerbated these effects.