Smc5/6 Is a Telomere-Associated Complex that Regulates Sir4 Binding and TPE

Smc proteins constitute the core members of the smc5/6,cohesin and condensin complexes. we demonstrate that smc5/6 is present at telomeres throughout the cell cycle and its association with chromosome ends is dependent on nse3,a subcomponent of the complex. cells harboring a temperature sensitive mutant,nse3-1,are defective in smc5/6 localization to telomeres and have slightly shorter telomeres. nse3 interacts physically and genetically with two rap1-binding factors,rif2 and sir4. reduction in telomere-associated smc5/6 leads to defects in telomere clustering,dispersion of the silencing factor,sir4,and a loss in transcriptional repression for sub-telomeric genes and non-coding telomeric repeat-containing rna (terra). sir4 recovery at telomeres is reduced in cells lacking smc5/6 functionality and vice versa. however,nse3-1/ sir4 δ double mutants show additive defects for telomere shortening and tpe indicating the contribution of smc5/6 to telomere homeostasis is only in partial overlap with sir factor silencing. these findings support a role for smc5/6 in telomere maintenance that is separate from its canonical role(s) in hr-mediated events during replication and telomere elongation. © 2016 moradi-fard et al.