title: Telomere maintenance through spatial control of telomeric proteins.
abstract: The six human telomeric proteins TRF1, TRF2, RAP1, TIN2, POT1, and TPP1 can form a complex called the telosome/shelterin, which is required for telomere protection and length control. TPP1 has been shown to regulate both POT1 telomere localization and telosome assembly through its binding to TIN2. It remains to be determined where such interactions take place and whether cellular compartmentalization of telomeric proteins is important for telomere maintenance. We systematically investigated here the cellular localization and interactions of human telomeric proteins. Interestingly, we found TIN2, TPP1, and POT1 to localize and interact with each other in both the cytoplasm and the nucleus. Unexpectedly, TPP1 contains a functional nuclear export signal that directly controls the amount of TPP1 and POT1 in the nucleus. Furthermore, binding of TIN2 to TPP1 promotes the nuclear localization of TPP1 and POT1. We also found that disrupting TPP1 nuclear export could result in telomeric DNA damage response and telomere length disregulation. Our findings highlight how the coordinated interactions between TIN2, TPP1, and POT1 in the cytoplasm regulate the assembly and function of the telosome in the nucleus and indicate for the first time the importance of nuclear export and spatial control of telomeric proteins in telomere maintenance.
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
authors.forename: Liuh-Yow
authors.initials: LY
authors.lastname: Chen
authors.forename: Dan
authors.initials: D
authors.lastname: Liu
authors.forename: Zhou
authors.initials: Z
authors.lastname: Songyang
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D006801:Humans; D051379:Mice; D008954:Models, Biological; D008969:Molecular Sequence Data; D049790:Nuclear Export Signals; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D000089804:Shelterin Complex; D016615:Telomere / Q000378:metabolism*; D034501:Telomere-Binding Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: C495876:ACD protein, human; C544060:Acd protein, mouse; D049790:Nuclear Export Signals; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins