[3][4] For both budding yeast and mammals, the CST complex contributes to telomere maintenance, but this function is more crucial for budding yeast, where the CST complex performs the functions that shelterin performs in vertebrates.
[1] At least four factors contribute to telomere maintenance: telomerase, shelterin, TERRA and the CST Complex.
[5] CST protection of telomeres for mammals occurs under conditions of replication stress.
But when not replicating DNA, mammals primarily require shelterin for telomere protection.
[3] In fungus, the CST complex has been shown to unfold higher order G-tailed structures, such as occur with telomere exposure during DNA replication.