Pif1 family helicases suppress genome instability at G-quadruplex motifs

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The Saccharomyces cerevisiae Pif1 helicase is the prototypical member of the Pif1 DNA helicase family, which is conserved from bacteria to humans. Here we show that exceptionally potent G-quadruplex unwinding is conserved among Pif1 helicases. Moreover, Pif1 helicases from organisms separated by more than 3 billion years of evolution suppressed DNA damage at G-quadruplex motifs in yeast. The G-quadruplex-induced damage generated in the absence of Pif1 helicases led to new genetic and epigenetic changes. Furthermore, when expressed in yeast, human PIF1 suppressed both G-quadruplex-associated DNA damage and telomere lengthening.

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Figure 1: Pif1 preferentially binds G4 DNA.
Figure 2: Pif1 helicases preferentially unwind G4 structures.
Figure 3: Effects of G4 motifs on GCRs.
Figure 4: Pif1 family helicases suppress G4-induced GCR events in pif1-m2 rrm3Δ+G4 cells.
Figure 5: Mechanism of CGE silencing and effect of Pif1 helicases on telomere length.


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We thank J. B. Boule for early work on S. cerevisiae Pif1 biochemistry, P. Opresko for the gift of purified human WRN, E. Allen-Vercoe, K. Bidle, C. Parker, R. Johnson, H. L. Ayala-del-Rio and E. Sockett for materials and for cloning non-yeast Pif1 helicases, and M. Platts for multiplex PCR and Southern analysis methods to characterize GCR clones. We acknowledge financial support from the National Institutes of Health (V.A.Z., S.C.K.), National Science Foundation (K.L.F.), DFG and NJCCR (K.P.) and American Cancer Society (M.L.B.).

Author information

K.P. and M.L.B. purified Pif1 helicases and performed biochemical and GCR experiments; P.D.G. and M.L.B. did the silencing experiments; P.C. purified Sgs1; S.C.K. aided in the analysis and interpretation of the biochemistry and provided purified E. coli RecQ; K.L.F. aided in the analysis and interpretation of GCR events; K.P., M.L.B. and V.A.Z. designed the study, analysed data and wrote the manuscript. K.P. and M.L.B. contributed equally. All authors discussed the results and commented on the manuscript.

Correspondence to Virginia A. Zakian.

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Paeschke, K., Bochman, M., Garcia, P. et al. Pif1 family helicases suppress genome instability at G-quadruplex motifs. Nature 497, 458–462 (2013) doi:10.1038/nature12149

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