Telomere protein complexes and interactions with telomerase in telomere maintenance

Telomeres are the termini of linear chromosomes. They are composed of DNA and DNA-binding proteins critical for maintaining chromosome integrity and cellular function. Telomere binding proteins regulate the structure and function of telomeres through the formation of different complexes with telomeric DNA. Double-and single-stranded telomeric DNA binding protein complexes have shared and unique functions that regulate telomere homeostasis. Recent studies have shown that telomerase interacts with several telomere-binding protein complexes including shelterin, CST, DNA-dependent protein kinase (DNA-PK) and MRN. The present review describes the recognised telomere-binding protein complexes, subcomplex exchanges and inter-complex molecular interactions. It also discusses the evidence suggesting that telomerase reverse transcriptase (TERT) switches between different complexes. Studies of the telomere protein intercomplex interactions and the switching of components between complexes provide insight into their fundamental roles of programming telomere length and configuration, and thus cell proliferative potential.