title: The human Pif1 helicase, a potential Escherichia coli RecD homologue, inhibits telomerase activity.
abstract: Telomeres, the protein-DNA complexes at the ends of eukaryotic chromosomes, are essential for chromosome stability, and their maintenance is achieved by the specialized reverse transcriptase activity of telomerase or the homologous recombination pathway in most eukaryotes. Here, we identified a human helicase, hPif1 that inhibits telomerase activity. The primary sequence and biochemical analysis suggest that hPif1 is a potential homologue of Escherichia coli RecD, an ATP-dependent 5' to 3' DNA helicase. Ectopic expression of wild-type, but not the ATPase/helicase-deficient hPif1, causes telomere shortening in HT1080 cells. hPif1 reduces telomerase processivity and unwinds DNA/RNA duplex in vitro. hPif1 preferentially binds telomeric DNA in vitro and in vivo. We propose that the mechanism of hPif1's inhibition on telomerase involves unwinding of the DNA/RNA duplex formed by telomerase RNA and telomeric DNA, and RecD homologues in eukaryotes may have evolved gaining additional functions.
authors.affiliation: Max-Planck Junior Research Group in the State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, The Graduate School, Chinese Academy of Sciences, Shanghai 200031, PR China.
authors.forename: Deng-Hong
authors.initials: DH
authors.lastname: Zhang
authors.forename: Bo
authors.initials: B
authors.lastname: Zhou
authors.forename: Yu
authors.initials: Y
authors.lastname: Huang
authors.forename: Lu-Xia
authors.initials: LX
authors.lastname: Xu
authors.forename: Jin-Qiu
authors.initials: JQ
authors.lastname: Zhou
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004265:DNA Helicases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry; D043211:Exodeoxyribonuclease V / Q000737:chemistry; D006801:Humans; D012313:RNA / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D019098:Telomerase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016615:Telomere / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D012313:RNA; D004247:DNA; D019098:Telomerase; D043211:Exodeoxyribonuclease V; C468322:exodeoxyribonuclease V, E coli; D000251:Adenosine Triphosphatases; D004265:DNA Helicases; C508765:PIF1 protein, human