Telomere recombination requires the MUS81 endonuclease

Abstract

Telomerase-negative cancer cells maintain their telomeres via the Alternative Lengthening of Telomeres (ALT) pathway1–3. 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, plays a key role in the maintenance of telomeres in human ALT cells. We find that MUS81 specifically localizes to ALT-associated promyelocytic leukemia nuclear bodies (APBs) and associates with telomeric DNA in ALT cells, which is enriched during G2 phase of the cell cycle. Depletion of MUS81 results in 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 TRF2 regulates this enzymatic activity to maintain telomere recombination. Thus, our results suggest that MUS81 is involved in the maintenance of ALT cell survival at least in part by telomere-HR process.

The MUS81 endonuclease is essential for telomerase negative cell proliferation

“…We find that TRF2 forms a complex with MUS81, inhibits the endonuclease activity of MUS81 by suppressing MUS81 binding to the DNA substrates, and mediates T-SCE through interaction with MUS81. 1 These findings, together with the fact that the MUS81 enzymatic activity is required for telomere recombination and ALT cell viability, support a model that TRF2 suppresses telomere recombination through regulation of the endonuclease activity of MUS81 in the ALT pathway (Fig. 2).…”

“…In our recent study, 1 we have demonstrated that the MUS81 endonuclease specifically localizes to APBs and associates with telomeric DNA in ALT cells, which is enriched during G 2 phase of the cell cycle ( Fig. 1).…”

“…1 We propose a model where telomeres move into APBs for processing recombination based telomere maintenance after DNA replication during G 2 phase of the cell cycle. MUS81 is recruited into recombination sites to cleave the recombination structure, for example, D-loop (Fig.…”

“…1 In yeast, MUS81 is required for the survival of cells undergoing aberrant replication and recombination. 22,24 However, the biological functions of MUS81 in human cells are largely unknown.…”

Mammalian BTBD12/SLX4 Assembles A Holliday Junction Resolvase and Is Required for DNA Repair

“…For example, the functions of ERCC4(XPF) in processing of telomere structures via TERF2 (Zhu et al, 2003) may be coordinated by SLX4, which has independently been found at telomeres (Dejardin and Kingston, 2009). Likewise, SLX4 may facilitate MUS81-dependent recombination at telomeres (Zeng et al, 2009) Moreover, our data indicate that PLK1 can phosphorylate SLX4, suggesting a possible role for this kinase in conferring cell cycle control via SLX4 function. An understanding of the roles played by PLK1, as well as the novel SLX4-binding protein C20orf94, will require further study.…”