RNA-dependent chromatin targeting of TET2 for endogenous retrovirus control in pluripotent stem cells

Ten-eleven translocation (TET) proteins play key roles in regulating the methylation status of DNA through oxidizing methylcytosines (5mC), generating 5-hydroxymethylcytosines (5hmC) that can both serve as stable epigenetic marks and participate in active demethylation. Unlike the other TET-family members, TET2 does not contain a DNA-binding domain, and it remains unclear how it is recruited to chromatin. Here we show that TET2 is recruited by the RNA-binding protein Paraspeckle component 1 (PSPC1) through transcriptionally active loci, including endogenous retroviruses (ERVs) whose long terminal repeats (LTRs) have been co-opted by mammalian genomes as stage- and tissue-specific transcriptional regulatory modules. We find that PSPC1 and TET2 contribute to ERVL and ERVL-associated gene regulation by both transcriptional repression via histone deacetylases and posttranscriptional destabilization of RNAs through 5hmC modification. Our findings provide evidence for a functional role of transcriptionally active ERVs as specific docking sites for RNA epigenetic modulation and gene regulation.