Article

Loss of Rap1 induces telomere recombination in the absence of NHEJ or a DNA damage signal.

The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
Science (Impact Factor: 31.48). 03/2010; 327(5973):1657-61. DOI: 10.1126/science.1185100
Source: PubMed

ABSTRACT Shelterin is an essential telomeric protein complex that prevents DNA damage signaling and DNA repair at mammalian chromosome ends. Here we report on the role of the TRF2-interacting factor Rap1, a conserved shelterin subunit of unknown function. We removed Rap1 from mouse telomeres either through gene deletion or by replacing TRF2 with a mutant that does not bind Rap1. Rap1 was dispensable for the essential functions of TRF2--repression of ATM kinase signaling and nonhomologous end joining (NHEJ)--and mice lacking telomeric Rap1 were viable and fertile. However, Rap1 was critical for the repression of homology-directed repair (HDR), which can alter telomere length. The data reveal that HDR at telomeres can take place in the absence of DNA damage foci and underscore the functional compartmentalization within shelterin.

0 Followers
 · 
103 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Telomere length homeostasis is essential for genomic stability and unlimited self-renewal of embryonic stem cells (ESCs). We show that telomere-associated protein Rif1 is required to maintain telomere length homeostasis by negatively regulating Zscan4 expression, a critical factor for telomere elongation by recombination. Depletion of Rif1 results in terminal hyperrecombination, telomere length heterogeneity, and chromosomal fusions. Reduction of Zscan4 by shRNA significantly rescues telomere recombination defects of Rif1-depleted ESCs and associated embryonic lethality. Further, Rif1 negatively modulates Zscan4 expression by maintaining H3K9me3 levels at subtelomeric regions. Mechanistically, Rif1 interacts and stabilizes H3K9 methylation complex. Thus, Rif1 regulates telomere length homeostasis of ESCs by mediating heterochromatic silencing.
    Developmental Cell 04/2014; 29(1):7-19. DOI:10.1016/j.devcel.2014.03.004 · 10.37 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: TRF2 is a component of shelterin, the protein complex that protects the ends of mammalian chromosomes. TRF2 is essential for telomere capping owing to its roles in suppressing an ATM-dependent DNA damage response (DDR) at chromosome ends and inhibiting end-to-end chromosome fusions. Mice deficient for TRF2 are early embryonic lethal. However, the role of TRF2 in later stages of development and in the adult organism remains largely unaddressed, with the exception of liver, where TRF2 was found to be dispensable for maintaining tissue function. Here, we study the impact of TRF2 conditional deletion in stratified epithelia by generating the TRF2∆/∆-K5-Cre mouse model, which targets TRF2 deletion to the skin from embryonic day E11.5. In marked contrast to TRF2 deletion in the liver, TRF2∆/∆-K5-Cre mice show lethality in utero reaching 100% lethality perinataly. At the molecular and cellular level, TRF2 deletion provokes induction of an acute DDR at telomeres, leading to activation of p53 signaling pathways and to programed cell death since the time of Cre expression at E11.5. Unexpectedly, neither inhibition of the NHEJ pathway by abrogation of 53BP1 nor inhibition of DDR by p53 deficiency rescued these severe phenotypes. Instead, TRF2 deletion provokes an extensive epidermal cell death accompanied by severe inflammation already at E16.5 embryos, which are independent of p53. These results are in contrast with conditional deletion of TRF1 and TPP1 in the skin, where p53 deficiency rescued the associated skin phenotypes, highlighting the comparatively more essential role of TRF2 in skin homeostasis.
    Aging cell 04/2014; 13(4). DOI:10.1111/acel.12221 · 5.94 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Telomeres are protected from nonhomologous end-joining (NHEJ) to avoid deleterious chromosome fusions, yet they associate with the Ku heterodimer that is principal in the classical NHEJ (c-NHEJ) pathway. T-loops have been proposed to inhibit Ku's association with telomeric ends, thus inhibiting c-NHEJ; however, deficiencies in the t-loop model suggest additional mechanisms are in effect. We demonstrate that TRF2 interacts with Ku at telomeres and via residues in Ku70 helix 5 (α5), which are vital for NHEJ. We show that Ku's interaction with a TRF2 mutant that induces telomeric fusions is significantly impaired. Additionally, we demonstrate that Ku70 α5 is required for Ku self-association in live cells, which can bridge DNA ends. Together, these findings lead us to propose a model in which telomeres are directly protected from c-NHEJ via TRF2 impeding Ku's ability to synapse telomere ends.
    Cell Reports 10/2013; 5(1). DOI:10.1016/j.celrep.2013.08.040 · 7.21 Impact Factor

Preview

Download
0 Downloads
Available from

Similar Publications