Preprint links Xist RNA localisation to chromosome compartment architecture during X-inactivation

A preprint on bioRxiv reports new mechanistic insight into how Xist RNA — the long non-coding RNA that orchestrates X-chromosome inactivation in mammals — localises across the inactive X chromosome in cis rather than spreading to other chromosomes.

The researchers developed cell models deficient for MCPH1, a protein whose loss causes chromosomes to remain in a compacted interphase state, making individual chromosome territories visually distinct. This system allowed them to track Xist RNA localisation relative to defined chromosomal sub-compartments. They report that Xist concentrates at sites around the periphery of compacted chromosome territories, and that these sites correspond closely to regions associated with the A1 sub-compartment — a nuclear organisation domain previously linked to active chromatin.

The findings suggest that the three-dimensional spatial architecture of chromosomes within the nucleus plays an active role in directing Xist spreading, rather than Xist simply diffusing in an unguided manner from its site of transcription. The in cis specificity of Xist localisation has been a longstanding open question in epigenetics and chromosome biology.

This work is a preprint and has not yet undergone peer review. It will be of interest to researchers working on X-chromosome inactivation, nuclear organisation, and the biology of long non-coding RNAs.