The yeast Pif1p DNA helicase preferentially unwinds RNA-DNA substrates

Jean Baptiste Boué, Virginia A. Zakian

Research output: Contribution to journalArticlepeer-review

137 Scopus citations


Pif1p is the prototypical member of the PIF1 family of DNA helicases, a subfamily of SFI helicases conserved from yeast to humans. Baker's yeast Pif1p is involved in the maintenance of mitochondrial, ribosomal and telomeric DNA and may also have a general role in chromosomal replication by affecting Okazaki fragment maturation. Here we investigate the substrate preferences for Pif1p. The enzyme was preferentially active on RNA-DNA hybrids, as seen by faster unwinding rates on RNA-DNA hybrids compared to DNA-DNA hybrids. When using forked substrates, which have been shown previously to stimulate the enzyme, Pif1p demonstrated a preference for RNA-DNA hybrids. This preferential unwinding could not be correlated to preferential binding of Pif1p to the substrates that were the most readily unwound. Although the addition of the single-strand DNA-binding protein replication protein A (RPA) stimulated the helicase reaction on all substrates, it did not diminish the preference of Pif1p for RNA-DNA substrates. Thus, forked RNA-DNA substrates are the favored substrates for Pif1p in vitro. We discuss these findings in terms of the known biological roles of the enzyme.

Original languageEnglish (US)
Pages (from-to)5809-5818
Number of pages10
JournalNucleic acids research
Issue number17
StatePublished - Sep 2007

All Science Journal Classification (ASJC) codes

  • Genetics


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