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A parallel quadruplex DNA is bound tightly but unfolded slowly by pif1 helicase.

ABSTRACT: 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 intramolecular quadruplex. Pif1 readily unfolds a parallel quadruplex DNA substrate in a multiturnover reaction and also generates 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 hydrolysis occurs at a faster rate than quadruplex unfolding, indicating that some ATP hydrolysis events are non-productive during unfolding of intramolecular parallel quadruplex DNA. However, product eventually accumulates at a slow rate.

SUBMITTER: Byrd AK

PROVIDER: S-EPMC4358282 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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A parallel quadruplex DNA is bound tightly but unfolded slowly by pif1 helicase.

Byrd Alicia K AK Raney Kevin D KD

The Journal of biological chemistry 20150114 10

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 intramolecular q ...[more]

PMID: 25589786

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