TEN1 is part of a complex that binds to single-stranded DNA and is necessary in order to protect telomeres from DNA degradation (CST complex). The CST complex binds single-stranded DNA with high affinity in a sequence-independent mode, while isolated subunits bind DNA with low affinity by themselves. Further to telomere protection, the CST complex has most likely a more general part in DNA metabolism at non-telomeric sites.