Defective Repair of Uracil Causes Telomere Defects in Mouse Hematopoietic Cells

• DOI: 10.1074/jbc.m114.607101
• Publication Date: 2015-01-09T05:32:53Z
• Authors: Haritha Vallabhaneni; Fang Zhou; Robert W. Maul; Jaya Sarkar; Jinhu Yin; Ming Lei; Lea Harrington; Patricia J. Gearhart; Yie Liu
• Keywords: Mice, Knockout; 0303 health sciences; Base Sequence; DNA Repair; Telomere-Binding Proteins; Telomere Homeostasis; Bone Marrow Cells; Telomere; Shelterin Complex; DNA-Binding Proteins; 03 medical and health sciences; Animals; Telomeric Repeat Binding Protein 2; Telomeric Repeat Binding Protein 1; Uracil; Uracil-DNA Glycosidase; Cells, Cultured; In Situ Hybridization, Fluorescence; Thymine; DNA Damage; Protein Binding

Uracil in the genome can result from misincorporation of dUTP instead of dTTP during DNA synthesis, and is primarily removed by uracil DNA glycosylase (UNG) during base excision repair. Telomeres contain long arrays of TTAGGG repeats and may be susceptible to uracil misincorporation. Using model telomeric DNA substrates, we showed that the position and number of uracil substitutions of thymine in telomeric DNA decreased recognition by the telomere single-strand binding protein, POT1. In primary mouse hematopoietic cells, uracil was detectable at telomeres, and UNG deficiency further increased uracil loads and led to abnormal telomere lengthening. In UNG-deficient cells, the frequencies of sister chromatid exchange and fragility in telomeres also significantly increased in the absence of telomerase. Thus, accumulation of uracil and/or UNG deficiency interferes with telomere maintenance, thereby underscoring the necessity of UNG-initiated base excision repair for the preservation of telomere integrity.