Together, our results reveal that shelterin is not a single static complex but two functional subcomplexes with distinct dynamics. Both subcomplexes are dimeric and bind every other telomeric nucleosome.

Building on this model, we demonstrate that TRF1 and TRF2 bind non-overlapping sites on telomeric chromatin, as they can’t compete each other from telomeres. Consistent with an in vitro observation by Hu et al. from @kellythd-nguyen.bsky.social group.

However, TRF2 and RAP1 are very dynamic, providing an evidence that shelterin exists predominantly at two distinct subcomplexes.

Using single-molecule imaging in living cells, we found that TRF1, TIN2, TPP1 and POT1 subunits display static behavior – tightly bound to telomeres.

We found ~25–30 copies of each shelterin protein at telomeres in HeLa cells. Surprisingly, in HeLa 1.3 cells with telomeres 5× longer, the number rises only modestly (~40), suggesting shelterin is more sparsely distributed on longer telomeres.

Chromosome ends are protected by shelterin complex, but its precise composition and dynamics remain unclear. Using CRISPR genome editing, we tagged all shelterin components at endogenous loci to define their telomeric copy number and dynamics—uncovering key insights into genome stability.

Very nice work!