3D chromatin structures associated with ncRNA <i>roX2</i> for hyperactivation and coactivation across the entire X chromosome.

Abstract

The three-dimensional (3D) organization of chromatin within the nucleus is crucial for gene regulation. However, the 3D architectural features that coordinate the activation of an entire chromosome remain largely unknown. We introduce an omics method, RNA-associated chromatin DNA-DNA interactions, that integrates RNA polymerase II (RNAPII)-mediated regulome with stochastic optical reconstruction microscopy to investigate the landscape of noncoding RNA <i>roX2</i>-associated chromatin topology for gene equalization to achieve dosage compensation. Our findings reveal that <i>roX2</i> anchors to the target gene transcription end sites (TESs) and spreads in a distinctive boot-shaped configuration, promoting a more open chromatin state for hyperactivation. Furthermore, <i>roX2</i> arches TES to transcription start sites to enhance transcriptional loops, potentially facilitating RNAPII convoying and connecting proximal promoter-promoter transcriptional hubs for synergistic gene regulation. These TESs cluster as <i>roX2</i> compartments, surrounded by inactive domains for coactivation of multiple genes within the <i>roX2</i> territory. In addition, <i>roX2</i> structures gradually form and scaffold for stepwise coactivation in dosage compensation.