Limits...
Telomeric recombination induced by dysfunctional telomeres.

Brault ME, Autexier C - Mol. Biol. Cell (2010)

Bottom Line: Telomeres and telomerase represent promising anticancer targets.However, 15% of cancer cells maintain their telomeres through alternative recombination-based mechanisms, and previous analyses showed that recombination-based telomere maintenance can be activated after telomerase inhibition.We determined whether telomeric recombination can also be promoted by telomere dysfunction.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada H3A 2B2.

ABSTRACT
Telomere maintenance is essential for cellular immortality, and most cancer cells maintain their telomeres through the enzyme telomerase. Telomeres and telomerase represent promising anticancer targets. However, 15% of cancer cells maintain their telomeres through alternative recombination-based mechanisms, and previous analyses showed that recombination-based telomere maintenance can be activated after telomerase inhibition. We determined whether telomeric recombination can also be promoted by telomere dysfunction. We report for the first time that telomeric recombination can be induced in human telomerase-positive cancer cells with dysfunctional telomeres.

Show MeSH

Related in: MedlinePlus

Increased formation of 53BP1- or p-ATMSer1981–containing TIFs in the MuA-hTR–expressing clones. (A) YCC-B2 parental, vector-containing, and MuA-hTR–expressing cells were coimmunostained with an antibody recognizing 53BP1 (BP13, green) and an antibody recognizing TRF1 (#370, red). 53BP1 is colocalized with TRF1, indicating telomere dysfunction–induced foci (yellow). (B) YCC-B2 cells were also coimmunostained with an antibody against the activated and phosphorylated (Ser1981) form of ATM (10H11.E12, green) and anti-TRF1 (#370, red). Telomere dysfunction–induced foci are shown in yellow. (C) Quantification of TIF-positive cells. Cells with three or more foci colocalizing with TRF1 were counted as TIF positive. For each cell type, 100 cells were counted. Data are mean ± standard error of the mean (SEM) for three independent experiments. Asterisks indicate statistical significance from vector-containing cells (***P < 0.001). (D) Relative telomerase activity was measured by TRAP using serial fivefold dilutions of protein extracts.
© Copyright Policy - creative-commons
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3020914&req=5

Figure 1: Increased formation of 53BP1- or p-ATMSer1981–containing TIFs in the MuA-hTR–expressing clones. (A) YCC-B2 parental, vector-containing, and MuA-hTR–expressing cells were coimmunostained with an antibody recognizing 53BP1 (BP13, green) and an antibody recognizing TRF1 (#370, red). 53BP1 is colocalized with TRF1, indicating telomere dysfunction–induced foci (yellow). (B) YCC-B2 cells were also coimmunostained with an antibody against the activated and phosphorylated (Ser1981) form of ATM (10H11.E12, green) and anti-TRF1 (#370, red). Telomere dysfunction–induced foci are shown in yellow. (C) Quantification of TIF-positive cells. Cells with three or more foci colocalizing with TRF1 were counted as TIF positive. For each cell type, 100 cells were counted. Data are mean ± standard error of the mean (SEM) for three independent experiments. Asterisks indicate statistical significance from vector-containing cells (***P < 0.001). (D) Relative telomerase activity was measured by TRAP using serial fivefold dilutions of protein extracts.

Mentions: MuA-hTR expression resulted in the formation of foci containing the DNA damage protein 53BP1 and the telomeric protein TRF1 (Figure 1A). TIFs containing the phosphorylated (Ser1981) form of ataxia telangiectasia mutated (ATM) were also observed in cells expressing MuA-hTR, consistent with deprotected telomeres (Figure 1B). Quantification of TIF-positive cells is reported in Figure 1C. Hence, the incorporation of mutant telomere repeats in YCC-B2 cells can elicit a primary DNA damage response at telomeres, but this response is insufficient to lead to apoptosis or senescence (Cerone et al., 2006). Instead, MuA-hTR–expressing cells maintained growth rates similar to parental and vector-containing cells despite extensive, continuous passaging for 3 mo. Persistence of mutant telomerase activity and mutant telomeric repeats confirmed that the mutants’ proliferation was not due to loss of MuA-hTR expression.FIGURE 1:


Telomeric recombination induced by dysfunctional telomeres.

Brault ME, Autexier C - Mol. Biol. Cell (2010)

Increased formation of 53BP1- or p-ATMSer1981–containing TIFs in the MuA-hTR–expressing clones. (A) YCC-B2 parental, vector-containing, and MuA-hTR–expressing cells were coimmunostained with an antibody recognizing 53BP1 (BP13, green) and an antibody recognizing TRF1 (#370, red). 53BP1 is colocalized with TRF1, indicating telomere dysfunction–induced foci (yellow). (B) YCC-B2 cells were also coimmunostained with an antibody against the activated and phosphorylated (Ser1981) form of ATM (10H11.E12, green) and anti-TRF1 (#370, red). Telomere dysfunction–induced foci are shown in yellow. (C) Quantification of TIF-positive cells. Cells with three or more foci colocalizing with TRF1 were counted as TIF positive. For each cell type, 100 cells were counted. Data are mean ± standard error of the mean (SEM) for three independent experiments. Asterisks indicate statistical significance from vector-containing cells (***P < 0.001). (D) Relative telomerase activity was measured by TRAP using serial fivefold dilutions of protein extracts.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3020914&req=5

Figure 1: Increased formation of 53BP1- or p-ATMSer1981–containing TIFs in the MuA-hTR–expressing clones. (A) YCC-B2 parental, vector-containing, and MuA-hTR–expressing cells were coimmunostained with an antibody recognizing 53BP1 (BP13, green) and an antibody recognizing TRF1 (#370, red). 53BP1 is colocalized with TRF1, indicating telomere dysfunction–induced foci (yellow). (B) YCC-B2 cells were also coimmunostained with an antibody against the activated and phosphorylated (Ser1981) form of ATM (10H11.E12, green) and anti-TRF1 (#370, red). Telomere dysfunction–induced foci are shown in yellow. (C) Quantification of TIF-positive cells. Cells with three or more foci colocalizing with TRF1 were counted as TIF positive. For each cell type, 100 cells were counted. Data are mean ± standard error of the mean (SEM) for three independent experiments. Asterisks indicate statistical significance from vector-containing cells (***P < 0.001). (D) Relative telomerase activity was measured by TRAP using serial fivefold dilutions of protein extracts.
Mentions: MuA-hTR expression resulted in the formation of foci containing the DNA damage protein 53BP1 and the telomeric protein TRF1 (Figure 1A). TIFs containing the phosphorylated (Ser1981) form of ataxia telangiectasia mutated (ATM) were also observed in cells expressing MuA-hTR, consistent with deprotected telomeres (Figure 1B). Quantification of TIF-positive cells is reported in Figure 1C. Hence, the incorporation of mutant telomere repeats in YCC-B2 cells can elicit a primary DNA damage response at telomeres, but this response is insufficient to lead to apoptosis or senescence (Cerone et al., 2006). Instead, MuA-hTR–expressing cells maintained growth rates similar to parental and vector-containing cells despite extensive, continuous passaging for 3 mo. Persistence of mutant telomerase activity and mutant telomeric repeats confirmed that the mutants’ proliferation was not due to loss of MuA-hTR expression.FIGURE 1:

Bottom Line: Telomeres and telomerase represent promising anticancer targets.However, 15% of cancer cells maintain their telomeres through alternative recombination-based mechanisms, and previous analyses showed that recombination-based telomere maintenance can be activated after telomerase inhibition.We determined whether telomeric recombination can also be promoted by telomere dysfunction.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada H3A 2B2.

ABSTRACT
Telomere maintenance is essential for cellular immortality, and most cancer cells maintain their telomeres through the enzyme telomerase. Telomeres and telomerase represent promising anticancer targets. However, 15% of cancer cells maintain their telomeres through alternative recombination-based mechanisms, and previous analyses showed that recombination-based telomere maintenance can be activated after telomerase inhibition. We determined whether telomeric recombination can also be promoted by telomere dysfunction. We report for the first time that telomeric recombination can be induced in human telomerase-positive cancer cells with dysfunctional telomeres.

Show MeSH
Related in: MedlinePlus