Ssu72 phosphatase is a conserved telomere replication terminator
Résumé
Telomeres, the protective ends of eukaryotic chromosomes, are replicated through concerted actions of conventional DNA poly-merases and elongated by telomerase, but the regulation of this process is not fully understood. Telomere replication requires (Ctc1/ Cdc13)-Stn1-Ten1, a telomeric ssDNA-binding complex homologous to RPA. Here, we show that the evolutionarily conserved phos-phatase Ssu72 is responsible for terminating the cycle of telomere replication in fission yeast. Ssu72 controls the recruitment of Stn1 to telomeres by regulating Stn1 phosphorylation at Ser74, a residue located within its conserved OB-fold domain. Consequently, ssu72Δ mutants are defective in telomere replication and exhibit long 3 0-ssDNA overhangs, indicative of defective lagging-strand DNA synthesis. We also show that hSSU72 regulates telomerase activation in human cells by controlling recruitment of hSTN1 to telomeres. These results reveal a previously unknown yet conserved role for the phosphatase SSU72, whereby this enzyme controls telomere homeostasis by activating lagging-strand DNA synthesis, thus terminating the cycle of telomere replication.
Origine : Publication financée par une institution
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