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Trf1 Is Not Required for Proliferation or Functional Telomere Maintenance in Chicken DT40 Cells
Authors:Carol Cooley  Katie M Baird  Virginie Faure  Thomas Wenner  Jillian L Stewart  Sonie Modino  Predrag Slijepcevic  Christine J Farr  and Ciaran G Morrison
Institution:*Centre for Chromosome Biology, National University of Ireland Galway, Department of Biochemistry and NCBES, Galway, Ireland; ;?Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom; and ;?Brunel Institute of Cancer Genetics and Pharmacogenomics, Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom
Abstract: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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