Search results for POT1

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Protein (1 results from a total of 1)

Identifier: R-HSA-174890
Species: Homo sapiens
Compartment: nucleoplasm
Primary external reference: UniProt: POT1: Q9NUX5

Reaction (4 results from a total of 4)

Identifier: R-HSA-9668831
Species: Homo sapiens
Compartment: nucleoplasm
CTC1, STN1 and TEN1, orthologs of S. cerrevisiae proteins Cdc13, Stn1 and Ten1, respectively, form the CST complex. This evolutionarily conserved complex plays a role in telomere maintenance (Miyake et al. 2009).
Identifier: R-HSA-181450
Species: Homo sapiens
Compartment: nucleoplasm
In addition to telomerase-mediated elongation and C-strand synthesis, other DNA processing steps are likely involved in telomere maintenance. In humans, nucleolytic activity is proposed to be involved in generating the G-rich 3' single strand overhang. In addition, differences in the structure of the overhang at telomeres that have undergone leading vs. lagging strand replication suggest that DNA processing may be different at these telomeres (Chai et al. 2006).

Many proteins associate with telomeric DNA. One complex that binds telomeres is called shelterin. Shelterin is a six-protein complex composed of TRF1 and TRF2, which can bind double-stranded telomeric DNA, POT1, which can bind single-stranded telomeric DNA, and three other factors, RAP1, TIN2, and TPP1 (reviewed in de Lange 2006 "Telomeres"). Human telomeric DNA is also bound by nucleosomes (Makarov et al. 1993; Nikitina and Woodcock 2004). A number of other proteins, including some that play roles in the DNA damage response, can be found at telomeres (Zhu et al. 2000; Verdun et al. 2005).

Studies in yeast and humans indicate that the association of many proteins with telomeres is regulated through the cell cycle (Zhu et al. 2000; Taggart et al. 2002; Fisher et al. 2004; Takata et al. 2004; Takata et al. 2005; Verdun et al. 2005). For instance, TRF1, MRE11, POT1, ATM, and NBS1 display cell cycle regulated chromatin immunoprecipitation of telomeric DNA (Zhu et al. 2000; Verdun et al. 2005), and cytologically observable hTERT and hTERC localize to a subset of telomeres only in S-phase (Jady et al. 2006; Tomlinson et al. 2006). These data indicate that telomeres are dynamically remodeled through the cell cycle.
Identifier: R-HSA-176700
Species: Homo sapiens
Compartment: nucleoplasm
In addition to telomerase-mediated elongation and C-strand synthesis, other DNA processing steps are likely involved in telomere maintenance. In humans, nucleolytic activity is proposed to be involved in generating the G-rich 3' single strand overhang. In addition, differences in the structure of the overhang at telomeres that have undergone leading vs. lagging strand replication suggest that DNA processing may be different at these telomeres (Chai et al. 2006).

Electron microscopy studies of purified human telomeric DNA have provided evidence for telomeric loops, or t-loops (Griffith et al. 1999). t-loops are proposed to result from invasion of the 3' G-rich single strand overhang into the double stranded portion of the telomeric TTAGGG repeat tract. The strand displaced by invasion forms a structure called a D loop. The function of the t-loop is presumed to be the protection of the 3' telomeric end. In vitro, the double strand telomeric DNA binding protein TRF2 can increase the frequency of t-loop formation. The prevalence of the t-loops in vivo is not known.

Many proteins associate with telomeric DNA. One complex that binds telomeres is called shelterin. Shelterin is a six-protein complex composed of TRF1 and TRF2, which can bind double-stranded telomeric DNA, POT1, which can bind single-stranded telomeric DNA, and three other factors, RAP1, TIN2, and TPP1 (reviewed in de Lange 2006 "Telomeres"). Human telomeric DNA is also bound by nucleosomes (Makarov et al. 1993; Nikitina and Woodcock 2004). A number of other proteins, including some that play roles in the DNA damage response, can be found at telomeres (Zhu et al. 2000; Verdun et al. 2005).

Studies in yeast and humans indicate that the association of many proteins with telomeres is regulated through the cell cycle (Smith et al. 1993; Zhu et al. 2000; Taggart et al. 2002; Fisher et al. 2004; Takata et al. 2004; Takata et al. 2005; Verdun et al. 2005). For instance, TRF1, MRE11, POT1, ATM, and NBS1 display cell cycle regulated chromatin immunoprecipitation of telomeric DNA (Zhu et al. 2000; Verdun et al. 2005), and cytologically observable hTERT and hTERC localize to a subset of telomeres only in S-phase (Jady et al. 2006; Tomlinson et al. 2006). These data indicate that telomeres are dynamically remodeled through the cell cycle.
Identifier: R-HSA-163096
Species: Homo sapiens
Compartment: nucleoplasm
Studies in yeast and human cells indicate that recruitment of telomerase to a telomere may be influenced by multiple variables, including regulatory protein factors, hTERT domains, telomere length, and the cell cycle stage. First, in yeast, the telomerase associated factor Est1 and the single-strand DNA binding protein Cdc13 play roles in telomerase recruitment (Pennock et al. 2001; Bianchi et al. 2004). Analogous proteins exist in human cells (Est1A, Est1B, Est1C, and POT1, respectively); however, how or whether these proteins are directly involved in telomerase recruitment remains to be elucidated. Second, N-terminal residues of hTERT within the DAT (dissociate the activities of telomerase) domain may have a role in binding single stranded telomeric DNA as the "anchor site" (Lee et al. 1993; Moriarty et al. 2005). Third, a cis-acting mechanism in yeast and humans that regulates telomere length maintenance may modulate telomerase access to the telomere (reviewed in Blackburn 2001; Smogorzewska and de Lange, 2004). Long telomeres, which have more associated protein factors, are in a state that is acted on by telomerase less frequently than that of short telomeres, which have fewer associated factors. Whether short telomeres actively recruit telomerase remains to be determined. Last, the recruitment of telomerase to telomeres shows cell-cycle regulation (Taggart et al. 2002; Smith et al. 2003; Fisher et al. 2004; Jady et al. 2006; Tomlinson et al. 2006). Presence of the telomeric protection complex shelterin at telomeres is necessary for the recruitment of telomerase. ACD (TPP1), the subunit of the shelterin complex, directly interacts, through its TEL patch region, with telomerase and is required for telomerase function in vivo (Abreu et al. 2010, Nandakumar et al. 2012, Sexton et al. 2014). The interaction involves the TEN domain of TERT (Schmidt et al. 2014).
The helicase RTEL1 is recruited to telomeres in S phase via direct interaction with the shelterin complex subunit TREF2. RTEL1 is needed for T-loop unwinding and resolution of telomeric G-quadruplex (G4) DNA structures, necessary steps for efficient telomere replication (Vannier et al. 2012, Sarek et al. 2015). Germline mutations in RTEL1 cause a severe form of dyskeratosis congenita, a telomere disorder syndrome, called Hoyeraal Hreidarsson syndrome (Ballew, Yeager et al. 2013; Walne et al. 2013; Ballew, Joseph et al. 2013, Le Guen et al. 2013, Deng et al. 2013). Loading of RTEL1 to telomere ends is negatively regulated outside of S phase by CDK2:CCNA-mediated phosphorylation of the shelterin complex subunit TERF2 at serine residue S365. At the S phase entry, TERF2 is dephosphorylated by the PP6 phosphatase, thus allowing timely RTEL1 loading (Sarek et al. 2019).
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