Telomeres, repetitive DNA sequences at chromosome ends, are shielded against the 
DNA damage response (DDR) by the shelterin complex. To understand how shelterin 
protects telomere ends, we investigated the structural organization of telomeric 
chromatin in human cells using super-resolution microscopy. We found that 
telomeres form compact globular structures through a complex network of 
interactions between shelterin subunits and telomeric DNA, but not by DNA 
methylation, histone deacetylation, or histone trimethylation at telomeres and 
subtelomeric regions. Mutations that abrogate shelterin assembly or removal of 
individual subunits from telomeres cause up to a 10-fold increase in telomere 
volume. Decompacted telomeres accumulate DDR signals and become more accessible 
to telomere-associated proteins. Recompaction of telomeric chromatin using an 
orthogonal method displaces DDR signals from telomeres. These results reveal the 
chromatin remodeling activity of shelterin and demonstrate that 
shelterin-mediated compaction of telomeric chromatin provides robust protection 
of chromosome ends against the DDR machinery.