Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Telomere recombination requires the MUS81 endonuclease


Telomerase-negative cancer cells maintain their telomeres through the alternative lengthening of telomeres (ALT) pathway1,2,3. Although a growing body of evidence demonstrates that the ALT mechanism is a post-replicative telomere recombination process, molecular details of this pathway are largely unknown. Here we demonstrate that MUS81, a DNA structure specific recombination endonuclease, has a key role in the maintenance of telomeres in human ALT cells. We find that MUS81 specifically localizes to ALT-associated promyelocytic leukaemia (PML) nuclear bodies (APBs) and associates with telomeric DNA in ALT cells, which is enriched during the G2 phase of the cell cycle. Depletion of MUS81 results in the reduction of ALT-specific telomere recombination and leads to proliferation arrest of ALT cells. In addition, the endonuclease activity of MUS81 is required for recombination-based ALT cell survival, and the interaction of MUS81 with the telomeric repeat-binding factor TRF2 regulates this enzymatic activity, thereby maintaining telomere recombination. Thus, our results suggest that MUS81 is involved in the maintenance of ALT cell survival at least in part by homologous recombination of telomeres.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: MUS81 localizes to APBs in ALT cells.
Figure 2: Depletion of MUS81 in ALT cells induces cell growth arrest and telomere loss, and decreases telomere recombination.
Figure 3: Expression of hTERT in ALT cells rescues cell growth from MUS81 depletion-mediated arrest.
Figure 4: MUS81 endonuclease activity is required for recombination-based ALT cell survival.
Figure 5: MUS81 interacts physically and functionally with TRF2.

Accession codes




  1. 1

    Dunham, M. A., Neumann, A. A., Fasching, C. L. & Reddel, R. R. Telomere maintenance by recombination in human cells. Nature Genet. 26, 447–450 (2000).

    CAS  Article  Google Scholar 

  2. 2

    Londono-Vallejo, J. A., Der-Sarkissian, H., Cazes, L., Bacchetti, S. & Reddel, R. R. Alternative lengthening of telomeres is characterized by high rates of telomeric exchange. Cancer Res. 64, 2324–2327 (2004).

    CAS  Article  Google Scholar 

  3. 3

    Wang, R. C., Smogorzewska, A. & de Lange, T. Homologous recombination generates T-loop-sized deletions at human telomeres. Cell 119, 355–368 (2004).

    CAS  Article  Google Scholar 

  4. 4

    Cesare, A. J. & Reddel, R. R. Telomere uncapping and alternative lengthening of telomeres. Mech. Ageing Dev. 129, 99–108 (2008).

    CAS  Article  Google Scholar 

  5. 5

    Bailey, S. M., Brenneman, M. A. & Goodwin, E. H. Frequent recombination in telomeric DNA may extend the proliferative life of telomerase-negative cells. Nucleic Acids Res. 32, 3743–3751 (2004).

    CAS  Article  Google Scholar 

  6. 6

    Yeager, T. R. et al. Telomerase-negative immortalized human cells contain a novel type of promyelocytic leukemia (PML) body. Cancer Res. 59, 4175–4179 (1999).

    CAS  PubMed  Google Scholar 

  7. 7

    Bryan, T. M., Englezou, A., Gupta, J., Bacchetti, S. & Reddel, R. R. Telomere elongation in immortal human cells without detectable telomerase activity. EMBO J. 14, 4240–4248 (1995).

    CAS  Article  Google Scholar 

  8. 8

    Muntoni, A. & Reddel, R. R. The first molecular details of ALT in human tumor cells. Hum. Mol. Genet. 14 Spec No. 2, R191–R196 (2005).

    CAS  Article  Google Scholar 

  9. 9

    Jiang, W. Q., Zhong, Z. H., Henson, J. D. & Reddel, R. R. Identification of candidate alternative lengthening of telomeres genes by methionine restriction and RNA interference. Oncogene 26, 4635–4647 (2007).

    CAS  Article  Google Scholar 

  10. 10

    Wu, G., Lee, W. H. & Chen, P. L. NBS1 and TRF1 colocalize at promyelocytic leukemia bodies during late S/G2 phases in immortalized telomerase-negative cells. Implication of NBS1 in alternative lengthening of telomeres. J. Biol. Chem. 275, 30618–30622 (2000).

    CAS  Article  Google Scholar 

  11. 11

    Grobelny, J. V., Godwin, A. K. & Broccoli, D. ALT-associated PML bodies are present in viable cells and are enriched in cells in the G(2)/M phase of the cell cycle. J. Cell Sci. 113 Pt 24, 4577–4585 (2000).

    CAS  PubMed  Google Scholar 

  12. 12

    Blais, V. et al. RNA interference inhibition of Mus81 reduces mitotic recombination in human cells. Mol. Biol. Cell 15, 552–562 (2004).

    CAS  Article  Google Scholar 

  13. 13

    Ehmsen, K. T. & Heyer, W. D. Saccharomyces cerevisiae Mus81-Mms4 is a catalytic, DNA structure-selective endonuclease. Nucleic Acids Res. 36, 2182–2195 (2008).

    CAS  Article  Google Scholar 

  14. 14

    Osman, F. & Whitby, M. C. Exploring the roles of Mus81-Eme1/Mms4 at perturbed replication forks. DNA Repair (Amst) 6, 1004–1017 (2007).

    CAS  Article  Google Scholar 

  15. 15

    Chen, X. B. et al. Human Mus81-associated endonuclease cleaves Holliday junctions in vitro. Mol. Cell 8, 1117–1127 (2001).

    CAS  Article  Google Scholar 

  16. 16

    Boddy, M. N. et al. Mus81-Eme1 are essential components of a Holliday junction resolvase. Cell 107, 537–548 (2001).

    CAS  Article  Google Scholar 

  17. 17

    Hollingsworth, N. M. & Brill, S. J. The Mus81 solution to resolution: generating meiotic crossovers without Holliday junctions. Genes Dev. 18, 117–125 (2004).

    CAS  Article  Google Scholar 

  18. 18

    Heyer, W. D. Recombination: Holliday junction resolution and crossover formation. Curr. Biol. 14, R56–R58 (2004).

    CAS  Article  Google Scholar 

  19. 19

    Gao, H., Chen, X. B. & McGowan, C. H. Mus81 endonuclease localizes to nucleoli and to regions of DNA damage in human S-phase cells. Mol. Biol. Cell 14, 4826–4834 (2003).

    CAS  Article  Google Scholar 

  20. 20

    Perrem, K., Colgin, L. M., Neumann, A. A., Yeager, T. R. & Reddel, R. R. Coexistence of alternative lengthening of telomeres and telomerase in hTERT-transfected GM847 cells. Mol. Cell. Biol. 21, 3862–3875 (2001).

    CAS  Article  Google Scholar 

  21. 21

    Cerone, M. A., Londono-Vallejo, J. A. & Bacchetti, S. Telomere maintenance by telomerase and by recombination can coexist in human cells. Hum. Mol. Genet. 10, 1945–1952 (2001).

    CAS  Article  Google Scholar 

  22. 22

    de Lange, T. Shelterin: the protein complex that shapes and safeguards human telomeres. Genes Dev. 19, 2100–2110 (2005).

    CAS  Article  Google Scholar 

  23. 23

    Palm, W. & de Lange, T. How shelterin protects mammalian telomeres. Annu. Rev. Genet. 42, 301–334 (2008).

    CAS  Article  Google Scholar 

  24. 24

    Griffith, J. D. et al. Mammalian telomeres end in a large duplex loop. Cell 97, 503–514 (1999).

    CAS  Article  Google Scholar 

  25. 25

    Stansel, R. M., de Lange, T. & Griffith, J. D. T-loop assembly in vitro involves binding of TRF2 near the 3′ telomeric overhang. EMBO J. 20, 5532–5540 (2001).

    CAS  Article  Google Scholar 

  26. 26

    Dendouga, N. et al. Disruption of murine Mus81 increases genomic instability and DNA damage sensitivity but does not promote tumorigenesis. Mol. Cell. Biol. 25, 7569–7579 (2005).

    CAS  Article  Google Scholar 

  27. 27

    Yang, Q., Zheng, Y. L. & Harris, C. C. POT1 and TRF2 cooperate to maintain telomeric integrity. Mol. Cell. Biol. 25, 1070–1080 (2005).

    CAS  Article  Google Scholar 

  28. 28

    Garcia-Cao, M., Gonzalo, S., Dean, D. & Blasco, M. A. A role for the Rb family of proteins in controlling telomere length. Nature Genet. 32, 415–419 (2002).

    CAS  Article  Google Scholar 

  29. 29

    Gonzalo, S. et al. DNA methyltransferases control telomere length and telomere recombination in mammalian cells. Nature Cell Biol. 8, 416–424 (2006).

    CAS  Article  Google Scholar 

  30. 30

    Karlseder, J., Smogorzewska, A. & de Lange, T. Senescence induced by altered telomere state, not telomere loss. Science 295, 2446–2449 (2002).

    CAS  Article  Google Scholar 

  31. 31

    Kaliraman, V., Mullen, J. R., Fricke, W. M., Bastin-Shanower, S. A. & Brill, S. J. Functional overlap between Sgs1-Top3 and the Mms4-Mus81 endonuclease. Genes Dev. 15, 2730–2740 (2001).

    CAS  Article  Google Scholar 

  32. 32

    Zhang, R. et al. BLM helicase facilitates Mus81 endonuclease activity in human cells. Cancer Res. 65, 2526–2531 (2005).

    CAS  Article  Google Scholar 

  33. 33

    Zou, L. & Elledge, S. J. Sensing DNA damage through ATRIP recognition of RPA-ssDNA complexes. Science 300, 1542–1548 (2003).

    CAS  Article  Google Scholar 

Download references


We thank R. R. Reddel for ALT cells, and C. H. McGowan for wild-type and mutant MUS81 constructs, the MUS81 antibody and Mus81 +/+ and Mus81−/− MEFs. We thank I. Hickson and J. Roti Roti for proof-reading. This work is supported in part by grants from Concern Foundation to Q.Y. and NIH CA10445/CA123232 to T.K.P. This research was also supported in part by the Intramural Research Program of the NIH, National Cancer Institute, Center for Cancer Research.

Author information




S.Z. performed most of the experiments; T.X performed immunoprecipitation-western assays and I.G.S. performed Q-FISH assay; T.K.P, S.G and C.C.H analysed data and Q.Y. planned the project, designed experiments, analysed data and wrote the paper.

Corresponding author

Correspondence to Qin Yang.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 1450 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Zeng, S., Xiang, T., Pandita, T. et al. Telomere recombination requires the MUS81 endonuclease. Nat Cell Biol 11, 616–623 (2009).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing