Table 4.
Comparative overview of proteins associated with telomeric single strand (ssDNA).
| Telomeric ssDNA Associated Proteins | |||||
|---|---|---|---|---|---|
| Human Telomeric ssDNA Associated Proteins | Protein Function and Direct Interactions | References | Arabidopsis Telomeric ssDNA Associated Proteins | Protein Function and Direct Interactions | References |
| POT1 | Shelterin. Int.: telomeric ssDNA, TPP1 and CTC1. | [50,51,52,53,54] | POT1a | Shelterin-like. Int.: TERT, telomeric ssDNA, TER1, TRFL9, CBF5, RuvBL1, CTC1 and STN1. | [47,55,56,57,58,69,105,189] |
| POT1b | Shelterin-like. Int.: TRB1, TER2, TER2s. | [56,82,100] | |||
| POT1c | POT1 paralogue of unknown function. | [47] | |||
| TERT | Catalytic subunit of telomerase. | [190] | TERT | Catalytic subunit of telomerase. | |
| STN1 | CST complex subunit, prevents G-overhang overextension. Int.: CTC1, TEN1, TPP1 and POLA. | [54,172,191,192] | STN1 | CST complex subunit, controls access of telomerase and DDR, together with POLA may be involved in C-strand synthesis. Int.: CTC1, TEN1 and POT1a. Non-telomeric function. Facilitates re-replication at non-telomeric loci. | [189,193,194,195] |
| TEN1 | CST complex subunit, involves C-strand fill-in synthesis. Int.: STN1. | [172,192] | TEN1 | CST complex subunit, controls access of telomerase and DDR, coordinating synthesis of the C-strand. Int.: STN1. | [194] |
| CTC1 | CST complex subunit, prevents G-overhang overextension. Int.: telomeric ssDNA, STN1, TPP1 and POT1. | [54,192] | CTC1 | CST complex subunit, controls access of the telomerase and DDR, coordinating synthesis of the C-strand. Int.: STN1, POT1a and POLA. | [171,189,196] |
| Purα | p.h. Unwinds dsDNA telomeric oligonucleotides. | [105] | PURα1 | Associates with TERT. | [84] |
| n.a. | Why1 | Regulates telomere-length homeostasis. Int.: telomeric ssDNA. | [197] | ||
| n.a. | STEP1 | Truncated derivative of chloroplast RNA-binding protein, role in plant telomere biogenesis. Int.: telomeric ssDNA. | [198] | ||
The proteins depicted in grey are involved in telomere maintenance, however, their association with telomeric ssDNA has not been fully proven yet. The proteins in green are structural homologues of their human/plant counterparts, however, any involvement in telomere maintenance or association with telomeric sequences has not been described so far. Direct interaction partners (Int.) interacting with telomeric ssDNA associated proteins are enumerated. Cases with not yet identified sequence homologues are denoted with n.a. Single strand DNA (ssDNA); Double-strand DNA (dsDNA); Cajal bodies factor 5 (CBF5); Conserved telomere maintenance component 1 (CTC1); CST complex (CTC1, STN1 and TEN1 subunits); DNA damage response (DDR); DNA polymerase alpha (POLA); Protection of telomeres 1 (POT1); Protection of telomeres 1a, b, c (POT1a, b, c); Pur-alpha 1 (Purα1); RuvB-like 1 (RuvBL1); Single-stranded telomere-binding protein 1 (STEP1); Suppressor of cdc thirteen homolog (STN1); Telomerase reverse transcriptase (TERT); Telomerase RNA subunit 1, 2, 2s (TER1, 2, 2s); Telomeric pathways in association with STN1 (TEN1); Telomeric repeat binding factor 1 -like 9 (TRFL9); TIN2- and POT1-organizing protein (TPP1); Whirly 1 (Why1); putative homolog according to NCBI blastp (p.h.).