Ku70 prevents genome instability resulting from heterozygosity of the telomerase RNA component in a vertebrate tumour line

Faure, Virginie; Wenner, Thomas; Cooley, Carol; Bourke, Emer; Farr, Carol L.; Takeda, Shunichi; Morrison, Ciarán

doi:10.1016/j.dnarep.2008.01.008

Cited by 8 publications

(9 citation statements)

References 50 publications

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“…The fact that several doublings are required before senescence occurs is consistent with gradual telomere attrition as a result of reduced telomerase activity, and this is certainly supported by the data in Fig. 5 A. Ku has, however, been implicated in protecting telomeres from nucleolytic degradation and aberrant recombination (Fisher and Zakian, 2005;Faure et al, 2008), and it is possible that some of the senescence-like features reflect an ability of the fusion proteins to impair these roles and therefore promote gross chromosomal rearrangements. It is also possible that they impair viability by interfering with the roles of Ku in transcriptional repression near telomeres or directing telomeres to the nuclear periphery (Fisher and Zakian, 2005).…”

Section: Discussionsupporting

confidence: 63%

Impaired telomerase activity in human cells expressing GFP-Ku86 fusion proteins

Badie

Yáñez‐Muñoz

Müller

et al. 2008

Cytogenet Genome Res

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The Ku heterodimer is a DNA end-binding protein that promotes the non-homologous end joining (NHEJ) pathway of DNA double strand break (DSB) repair by recruiting the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs). Ku is also a normal component of telomeres where it is required for telomere maintenance, interacting not only with the DNA but also with various telomere proteins including telomerase. The way in which Ku simultaneously plays such distinct roles, end-joining at DSBs and end-maintenance at telomeres, is unclear. One way to address this is to study cells in which the NHEJ and telomeric roles of Ku have been separated. Here we describe human cells that express fusions between the large human Ku subunit (Ku86) and a fluorescent protein tag. These cells have reduced telomerase activity and increased sensitivity to ionizing radiation (IR) but no change in their DNA-PK activity or in the DNA end-binding of endogenous Ku. Cells with particularly large amounts of one fusion protein undergo progressive telomere shortening and cellular senescence. These data are consistent with models in which Ku recruits telomerase to telomeres or activates recruited telomerase and suggest that the Ku86 fusion proteins specifically block this role.

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Section: Discussionsupporting

confidence: 63%

Impaired telomerase activity in human cells expressing GFP-Ku86 fusion proteins

Badie

Yáñez‐Muñoz

Müller

et al. 2008

Cytogenet Genome Res

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“…interstitial sequences and is not an optimal measure of telomere length (Venkatesan and Price, 1998), it can detect severe reductions in telomere length, as in Ku70-deficient TR ϩ/Ϫ DT40 cells (Faure et al, 2008). When we measured the length of the TRF fragments in the native gel, we noted a distinct clonal variation in telomere length that occurred over time ( Figure 3E).…”

Section: Resultsmentioning

confidence: 96%

“…Protein extracts from DT40 cells were assayed for telomerase activity using the PCR-based telomeric repeat amplification protocol (TRAP) assay (Kim and Wu, 1997) as described (Faure et al, 2008).…”

Section: Telomerase Activity Assaymentioning

confidence: 99%

Trf1 Is Not Required for Proliferation or Functional Telomere Maintenance in Chicken DT40 Cells

Cooley

Baird

Faure

et al. 2009

MBoC

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The telomere end-protection complex prevents the ends of linear eukaryotic chromosomes from degradation or inappropriate DNA repair. The homodimeric double-stranded DNA-binding protein, Trf1, is a component of this complex and is essential for mouse embryonic development. To define the requirement for Trf1 in somatic cells, we deleted Trf1 in chicken DT40 cells by gene targeting. Trf1-deficient cells proliferated as rapidly as control cells and showed telomeric localization of Trf2, Rap1, and Pot1. Telomeric G-strand overhang lengths were increased in late-passage Trf1-deficient cells, although telomere lengths were unaffected by Trf1 deficiency, as determined by denaturing Southern and quantitative FISH analysis. Although we observed some clonal variation in terminal telomere fragment lengths, this did not correlate with cellular Trf1 levels. Trf1 was not required for telomere seeding, indicating that de novo telomere formation can proceed without Trf1. The Pin2 isoform and a novel exon 4, 5-deleted isoform localized to telomeres in Trf1-deficient cells. Trf1-deficient cells were sensitive to DNA damage induced by ionizing radiation. Our data demonstrate that chicken DT40 B cells do not require Trf1 for functional telomere structure and suggest that Trf1 may have additional, nontelomeric roles involved in maintaining genome stability.

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“…This set of genes had an average coverage rate (0.86; Table 1) above that for all genes (0.81), indicating that the absence of the detection of nonsynonymous SNPs segregating in chicken was not due to poorer coverage. This group contained an immunity-related helicase (KU70; McDonald-Kreitman test p = 0.021) and a DNA polymerase (eta; p = 1.8 × 10 -5 ) involved in homologous recombination during DNA repair [23] and synthesis [24], respectively.…”

Section: Resultsmentioning

confidence: 99%

Evidence of the adaptive evolution of immune genes in chicken

et al. 2009

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The basis for understanding the characteristics of gene functional categories in chicken has been enhanced by the ongoing sequencing of the zebra finch genome, the second bird species to be extensively sequenced. This sequence provides an avian context for examining how variation in chicken has evolved since its divergence from its common ancestor with zebra finch as well as well as a calibrating point for studying intraspecific diversity within chicken. Immune genes have been subject to many selective processes during their evolutionary history: this gene class was investigated here in a set of orthologous chicken and zebra finch genes with functions assigned from the human ortholog. Tests demonstrated that nonsynonymous sites at immune genes were highly conserved both in chicken and on the avian lineage. McDonald-Kreitman tests provided evidence of adaptive evolution and a higher rate of selection on fixation of nonsynonymous substitutions at immune genes compared to that at non-immune genes. Further analyses showed that GC content was much higher in chicken than in zebra finch genes, and was significantly elevated in both species' immune genes. Pathogen challenges are likely to have driven the selective forces that have shaped variation at chicken immune genes, and continue to restrict diversity in this functional class.

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Ku70 prevents genome instability resulting from heterozygosity of the telomerase RNA component in a vertebrate tumour line

Cited by 8 publications

References 50 publications

Impaired telomerase activity in human cells expressing GFP-Ku86 fusion proteins

Impaired telomerase activity in human cells expressing GFP-Ku86 fusion proteins

Trf1 Is Not Required for Proliferation or Functional Telomere Maintenance in Chicken DT40 Cells

Evidence of the adaptive evolution of immune genes in chicken

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