Figure 1: Perinuclear and motor protein complexes ensure subtelomeric DSB survival.
From: Perinuclear tethers license telomeric DSBs for a broad kinesin- and NPC-dependent DNA repair process
(a) Schematic illustrating galactose-inducible DSB site within a subtelomeric (SubTEL) and internal region of Chromosome (Chr.) XI. (b) Genetic analysis of subtelomeric DSB survival. Survival (mean±s.d.; N=5) is compiled and presented as the ratio of colony-forming units on galactose (GAL) relative to glucose (GLU). Presented immediately above mutants are P values (t-test) relative to wild type. Other P values are as illustrated on the graph. Relative survival is in Supplementary Table 1. (c) Proportions of survivors (mean±s.d.; N=30) using BIR or NHEJ are revealed by PCR analysis using primers amplifying regions surrounding the DSB site. Error bars for overall survival rate are shown. (d,e) Representative subtelomeric DSB survivor analysis. (d) Agarose gels with corresponding primer pairs used right below showing how different PCR products amplified across the DSB site after induction/survival indicate different repair pathways. Survivors were initially analysed and categorized into BIR (no product), NHEJ (∼0.7 kb product) or incomplete DSB (∼2 kb product; very rare). All BIR survivors were subsequently analysed using a generic telomere AC1-3 primer with a small fraction of survivors yielding products. All PCR products were amplified using their respective primers as illustrated (P1* used for zip/control sequence strains for initial analysis). (e) EtBr-stained CHEF gel showing changes to the size of Chr. XI in wild-type BIR survivors relative to uninduced and NHEJ survivors. (f–h) Compiled subtelomeric or internal DSB survival assays reveal that survival of a subtelomeric, but not an internal, DSB located on the left arm of Chr. XI is dependent on cohibin/Esc1, Cik1 and Nup84 proteins (mean±s.d.; N=5). P values (t-test) comparing mutants to wild-type cells are immediately above bars with additional statistical comparisons as shown. (f) Disruption of telomeric SIR proteins increases Rad52-dependent survival of a subtelomeric DSB. (g) Deletion of the NHEJ factors Ku70/Dnl4 or SIR proteins, but not telomere tethers, motor proteins nor NPC components, decreases survival of an internal DSB. (h) Disruption of the Slx5–Slx8 complex compromises both subtelomeric and internal DSB survival.
