Epigenetic control of telomeric RNA maintains heterochromatin in telomerase-driven cancers [ChIP-Seq]

Depletion of FTSJ3 selectively impaired the viability of hTERT-positive cancer cells while sparing normal cells. Mechanistically, FTSJ3 installs 2′-O-methylation on the telomeric RNA TERRA, a modification essential for TERRA stability and function. Loss of FTSJ3 destabilizes TERRA, disrupts recruitment of the histone methyltransferase SUV39H1, and diminishes H3K9 trimethylation and HP1 assembly at sub-telomeric regions.

This breakdown of repressive telomeric chromatin leads to genome instability and apoptosis specifically in hTERT-positive cells. These findings highlight SDL as a powerful strategy for uncovering telomerase-dependent liabilities and establish FTSJ3 as a central regulator of telomere stability in telomerase-active cancers. Targeting FTSJ3 enzymatic activity offers a promising therapeutic entry point, acting upstream of TERRA to eliminate telomerase-driven malignancies selectively.