Waking the sleepers: lincRNA overexpression compromises DHX36 activity and global protein synthesis

Transposable element-derived long intergenic noncoding RNAs are increasingly recognized as context-dependent regulators of gene expression, but the functional consequences of their ectopic activation in somatic cells remain poorly understood. We previously showed that U7 snRNA represses a subset of LTR12-associated lincRNAs, including lnc-ARRDC4-1 and lnc-ADCYAP1-2, two testis-enriched lincRNAs with minimal expression in somatic cells. Here, we examined the consequences of their increased expression in somatic cells. We showed that overexpression of either lincRNA led to overlapping transcriptomic and proteomic changes, impaired migration, altered adhesion and proliferation, and a [~]50% reduction in protein synthesis. Furthermore, we identified lnc-ARRDC4-1 as an upstream regulator of lnc-ADCYAP1-2 transcription. Downstream of this event, lnc-ADCYAP1-2 interacts with the RNA helicase DHX36, a regulator of G-quadruplex-containing mRNAs. lnc-ADCYAP1-2 activation reduces DHX36 protein levels which is accompanied by decreased protein output from a subset of DHX36 mRNA targets. At the cellular level, these effects correlate with altered cell proliferation, migration, adhesion, and global translation. Our results suggest a lnc-ARRDC4-1: lnc-ADCYAP1-2 : DHX36 regulatory cascade linking de-repression of LTR12-containing lincRNAs to reduced protein synthesis and altered cellular processes in somatic cells.