Human POT1 is required for efficient telomere C-rich strand replication in the absence of WRN |
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Authors: | Nausica Arnoult Carole Saintome Isabelle Ourliac-Garnier Jean-Fran?ois Riou Arturo Londo?o-Vallejo |
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Institution: | 1.Telomeres and Cancer Laboratory, Institut Curie, Paris 75248, France;;2.Université Pierre et Marie Curie, Université Paris 06, Paris F-75005, France;;3.CNRS-UMR3244, Paris 75248, France;;4.Nucleic Acids Functions and Interactions, ANBioPHY, FRE3207 Université Pierre et Marie Curie CNRS, Paris 75252, France;;5.Muséum National d''Histoire Naturelle, USM 503, INSERM U565, CNRS UMR 7196, Paris 75005, France |
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Abstract: | Mechanisms of telomere replication remain poorly defined. It has been suggested that G-rich telomeric strand replication by lagging mechanisms requires, in a stochastic way, the WRN protein. Here we show that this requirement is more systematic than previously thought. Our data are compatible with a situation in which, in the absence of WRN, DNA synthesis at replication forks is uncoupled, thus allowing replication to continue on the C strand, while single G strands accumulate. We also show that in cells in which both WRN and POT1 are limiting, both G- and C-rich telomeric strands shorten, suggesting a complete replication block. Under this particular condition, expression of a fragment spanning the two POT1-OB (oligonucleotide-binding) fold domains is able to restore C (but not G) strand replication, suggesting that binding of POT1 to the lagging strand allows DNA synthesis uncoupling in the absence of WRN. Furthermore, in vitro experiments indicate that purified POT1 has a higher affinity for the telomeric G-rich strand than purified RPA. We propose a model in which the relative enrichments of POT1 versus RPA on the telomeric lagging strand allows or does not allow uncoupling of DNA synthesis at the replication fork. Our study reveals an unanticipated role for hPOT1 during telomere replication. |
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Keywords: | Telomeres replication POT1 WRN lagging leading |
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