title: POT1 stimulates RecQ helicases WRN and BLM to unwind telomeric DNA substrates.
abstract: Defects in human RecQ helicases WRN and BLM are responsible for the cancer-prone disorders Werner syndrome and Bloom syndrome. Cellular phenotypes of Werner syndrome and Bloom syndrome, including genomic instability and premature senescence, are consistent with telomere dysfunction. RecQ helicases are proposed to function in dissociating alternative DNA structures during recombination and/or replication at telomeric ends. Here we report that the telomeric single-strand DNA-binding protein, POT1, strongly stimulates WRN and BLM to unwind long telomeric forked duplexes and D-loop structures that are otherwise poor substrates for these helicases. This stimulation is dependent on the presence of telomeric sequence in the duplex regions of the substrates. In contrast, POT1 failed to stimulate a bacterial 3'-5'-helicase. We find that purified POT1 binds to WRN and BLM in vitro and that full-length POT1 (splice variant 1) precipitates a higher amount of endogenous WRN protein, compared with BLM, from the HeLa nuclear extract. We propose roles for the cooperation of POT1 with RecQ helicases WRN and BLM in resolving DNA structures at telomeric ends, in a manner that protects the telomeric 3' tail as it is exposed during unwinding.
authors: Laboratory of Molecular Gerontology, National Institute on Aging, Baltimore, Maryland 21224, USA.
authors: Patricia L
authors: PL
authors: Opresko
authors: Penelope A
authors: PA
authors: Mason
authors: Elaine R
authors: ER
authors: Podell
authors: Ming
authors: M
authors: Lei
authors: Ian D
authors: ID
authors: Hickson
authors: Thomas R
authors: TR
authors: Cech
authors: Vilhelm A
authors: VA
authors: Bohr
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D017398:Alternative Splicing; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000737:chemistry*; D004265:DNA Helicases / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005090:Exodeoxyribonucleases; D005092:Exonucleases / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D053484:RecQ Helicases; D011994:Recombinant Proteins / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D000089804:Shelterin Complex; D016615:Telomere / Q000648:ultrastructure*; D034501:Telomere-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D013696:Temperature; D013997:Time Factors; D000071657:Werner Syndrome Helicase
chemical_list: C440849:POT1 protein, human; D011994:Recombinant Proteins; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins; D004247:DNA; D005982:Glutathione Transferase; D005090:Exodeoxyribonucleases; D005092:Exonucleases; D000251:Adenosine Triphosphatases; C097151:Bloom syndrome protein; C506725:RECQL protein, human; D004265:DNA Helicases; D053484:RecQ Helicases; C098785:WRN protein, human; D000071657:Werner Syndrome Helicase