RTEL1 contributes to DNA replication and repair and telomere maintenance

Telomere maintenance and DNA repair are important processes that protect the genome against instability. mRtel1, an essential helicase, is a dominant factor setting telomere length in mice. In addition, mRtel1 is involved in DNA double-strand break repair. The role of mRtel1 in telomere maintenance and genome stability is poorly understood. Therefore we used mRtel1-deficient mouse embryonic stem cells to examine the function of mRtel1 in replication, DNA repair, recombination, and telomere maintenance. mRtel1-deficient mouse embryonic stem cells showed sensitivity to a range of DNA-damaging agents, highlighting its role in replication and genome maintenance. Deletion of mRtel1 increased the frequency of sister chromatid exchange events and suppressed gene replacement, demonstrating the involvement of the protein in homologous recombination. mRtel1 localized transiently at telomeres and is needed for efficient telomere replication. Of interest, in the absence of mRtel1, telomeres in embryonic stem cells appeared relatively stable in length, suggesting that mRtel1 is required to allow extension by telomerase. We propose that mRtel1 is a key protein for DNA replication, recombination, and repair and efficient elongation of telomeres by telomerase

RTEL1 contributes to DNA replication and repair and telomere maintenance

Telomere maintenance and DNA repair are important processes that protect the genome against instability. mRtel1, an essential helicase, is a dominant factor setting telomere length in mice. In addition, mRtel1 is involved in DNA double-strand break repair. The role of mRtel1 in telomere maintenance and genome stability is poorly understood. Therefore we used mRtel1-deficient mouse embryonic stem cells to examine the function of mRtel1 in replication, DNA repair, recombination, and telomere maintenance. mRtel1-deficient mouse embryonic stem cells showed sensitivity to a range of DNA-damaging agents, highlighting its role in replication and genome maintenance. Deletion of mRtel1 increased the frequency of sister chromatid exchange events and suppressed gene replacement, demonstrating the involvement of the protein in homologous recombination. mRtel1 localized transiently at telomeres and is needed for efficient telomere replication. Of interest, in the absence of mRtel1, telomeres in embr

Telomere resolution and genomic instability in mouse embryonic stem cells

Proper segregation of replicated chromosomes is essential for cell division in all organisms. Linear eukaryotic chromosomes contain specialized protective structures at the chromosome ends, called telomeres, which are essential for maintaining genome stability. Telomere associations have been observed during key cellular processes including mitosis, meiosis and carcinogenesis. These telomere associations need to be resolved prior to cell division to avoid loss of telomere function. TRF1, a core component of the telomere protein complex shelterin, has been implicated as a mediator of telomere associations. To determine the effect of TRF1 protein levels on telomere associations, we used live-cell fluorescence microscopy to visualize telomeres and chromosome dynamics in cells expressing defined levels of TRF1. Elevated levels of TRF1 induced anaphase bridges containing thin “thread-like” stretches of TRF1 foci connecting segregating chromosomes. We also observed telomere aggregates, mitotic bypass, and TRF1 bridges persisting into the following cell cycle. To examine the role of TRF1 in these telomere associations, we generated a TRF1 protein which can be inducibly cleaved by TEV protease. Telomere aggregates appeared to resolve upon cleavage of TRF1 proteins, suggesting that telomere associations result primarily from protein interactions mediated by TRF1. The essential helicase RTEL1 was observed at the extremities of persistent TRF1 bridges, possibly indicating a function for RTEL1 in the resolution of TRF1-induced telomere associations. Taken together, our results demonstrate that precise regulation of TRF1 levels is essential for telomere resolution and mitotic segregation.Medicine, Faculty ofMedicine, Department ofExperimental Medicine, Division ofGraduat

Resolution of telomere associations by TRF1 cleavage in mouse embryonic stem cells

Telomere associations have been observed during key cellular processes such as mitosis, meiosis, and carcinogenesis and must be resolved before cell division to prevent genome instability. Here we establish that telomeric repeat-binding factor 1 (TRF1), a core component of the telomere protein complex, is a mediator of telomere associations in mammalian cells. Using live-cell imaging, we show that expression of TRF1 or yellow fluorescent protein (YFP)-TRF1 fusion protein above endogenous levels prevents proper telomere resolution during mitosis. TRF1 overexpression results in telomere anaphase bridges and aggregates containing TRF1 protein and telomeric DNA. Site-specific protein cleavage of YFP-TRF1 by tobacco etch virus protease resolves telomere aggregates, indicating that telomere associations are mediated by TRF1. This study provides novel insight into the formation and resolution of telomere associations