Replicated sister chromatids are held together until mitosis by cohesin, a 
conserved multisubunit complex comprised of Smc1, Smc3, Scc1, and Scc3, which in 
vertebrate cells exists as two closely related homologues (SA1 and SA2). Here, 
we show that cohesin(SA1) and cohesin(SA2) are differentially required for 
telomere and centromere cohesion, respectively. Cells deficient in SA1 are 
unable to establish or maintain cohesion between sister telomeres after DNA 
replication in S phase. The same phenotype is observed upon depletion of the 
telomeric protein TIN2. In contrast, in SA2-depleted cells telomere cohesion is 
normal, but centromere cohesion is prematurely lost. We demonstrate that loss of 
telomere cohesion has dramatic consequences on chromosome morphology and 
function. In the absence of sister telomere cohesion, cells are unable to repair 
chromatid breaks and suffer sister telomere loss. Our studies elucidate the 
functional distinction between the Scc3 homologues in human cells and further 
reveal an essential role for sister telomere cohesion in genomic integrity.