Epigenetic regulation of human non-coding RNA gene transcription

Recent investigations on the non-protein-coding transcriptome of human cells have revealed previously hidden layers of gene regulation relying on regulatory non-proteincoding (nc) RNAs, including the widespread ncRNA-dependent regulation of epigenetic chromatin states and of mRNA translation and stability. However, despite its centrality, the epigenetic regulation of ncRNA genes has received relatively little attention. In this mini-review, we attempt to provide a synthetic account of recent literature suggesting an unexpected complexity in chromatin-dependent regulation of ncRNA gene transcription by the three human nuclear RNA polymerases. Emerging common features, like the heterogeneity of chromatin states within ncRNA multigene families and their influence on 3D genome organization, point to unexplored issues whose investigation could lead to a better understanding of the whole human epigenomic network.