A parallel quadruplex DNA is bound tightly but unfolded slowly by Pif1 helicase. Byrd, A. K. & Raney, K. D. Journal of Biological Chemistry, 290(10):6482–6494, 2015. tex.ids= byrdParallelQuadruplexDNA2015 ISBN: 1083-351X (Electronic) 0021-9258 (Linking)doi abstract bibtex Background: Some G-rich sequences fold into intramolecular quadruplex structures. Pif1 helicase reduces genomic insta-bility by unfolding quadruplex DNA. Results: Pif1 unfolds a parallel quadruplex structure slowly relative to unwinding of duplex DNA. Conclusion: Comparison of duplex unwinding to quadruplex unfolding is complicated by distinct kinetic mechanisms. Significance: A highly stable, intramolecular quadruplex is a formidable obstacle but can be overcome by Pif1 helicase. DNA sequences that can form intramolecular quadruplex structures are found in promoters of proto-oncogenes. Many of these sequences readily fold into parallel quadruplexes. Here we characterize the ability of yeast Pif1 to bind and unfold a parallel quadruplex DNA substrate. We found that Pif1 binds more tightly to the parallel quadruplex DNA than single-stranded DNA or tailed duplexes. However, Pif1 unwinding of duplexes occurs at a much faster rate than unfolding of a parallel intra-molecular quadruplex. Pif1 readily unfolds a parallel quadru-plex DNA substrate in a multiturnover reaction and also gener-ates some product under single cycle conditions. The rate of ATP hydrolysis by Pif1 is reduced when bound to a parallel quadruplex compared with single-stranded DNA. ATP hydro-lysis occurs at a faster rate than quadruplex unfolding, indicat-ing that some ATP hydrolysis events are non-productive during unfolding of intramolecular parallel quadruplex DNA. How-ever, product eventually accumulates at a slow rate.
@article{Byrd2015,
title = {A parallel quadruplex {DNA} is bound tightly but unfolded slowly by {Pif1} helicase},
volume = {290},
issn = {1083351X},
doi = {10.1074/jbc.M114.630749},
abstract = {Background: Some G-rich sequences fold into intramolecular quadruplex structures. Pif1 helicase reduces genomic insta-bility by unfolding quadruplex DNA. Results: Pif1 unfolds a parallel quadruplex structure slowly relative to unwinding of duplex DNA. Conclusion: Comparison of duplex unwinding to quadruplex unfolding is complicated by distinct kinetic mechanisms. Significance: A highly stable, intramolecular quadruplex is a formidable obstacle but can be overcome by Pif1 helicase. DNA sequences that can form intramolecular quadruplex structures are found in promoters of proto-oncogenes. Many of these sequences readily fold into parallel quadruplexes. Here we characterize the ability of yeast Pif1 to bind and unfold a parallel quadruplex DNA substrate. We found that Pif1 binds more tightly to the parallel quadruplex DNA than single-stranded DNA or tailed duplexes. However, Pif1 unwinding of duplexes occurs at a much faster rate than unfolding of a parallel intra-molecular quadruplex. Pif1 readily unfolds a parallel quadru-plex DNA substrate in a multiturnover reaction and also gener-ates some product under single cycle conditions. The rate of ATP hydrolysis by Pif1 is reduced when bound to a parallel quadruplex compared with single-stranded DNA. ATP hydro-lysis occurs at a faster rate than quadruplex unfolding, indicat-ing that some ATP hydrolysis events are non-productive during unfolding of intramolecular parallel quadruplex DNA. How-ever, product eventually accumulates at a slow rate.},
number = {10},
journal = {Journal of Biological Chemistry},
author = {Byrd, Alicia K. and Raney, Kevin D.},
year = {2015},
pmid = {25589786},
note = {tex.ids= byrdParallelQuadruplexDNA2015
ISBN: 1083-351X (Electronic) 0021-9258 (Linking)},
pages = {6482--6494},
}
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