title: Yeast Helicase Pif1 Unwinds RNA:DNA Hybrids with Higher Processivity than DNA:DNA Duplexes.
abstract: Saccharomyces cerevisiae Pif1, an SF1B helicase, has been implicated in both mitochondrial and nuclear functions. Here we have characterized the preference of Pif1 for RNA:DNA heteroduplexes in vitro by investigating several kinetic parameters associated with unwinding. We show that the preferential unwinding of RNA:DNA hybrids is due to neither specific binding nor differences in the rate of strand separation. Instead, Pif1 is capable of unwinding RNA:DNA heteroduplexes with moderately greater processivity compared with its duplex DNA:DNA counterparts. This higher processivity of Pif1 is attributed to slower dissociation from RNA:DNA hybrids. Biologically, this preferential role of the helicase may contribute to its functions at both telomeric and nontelomeric sites.
authors.affiliation: From the Department of Biochemistry and Molecular Biology University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205.
authors.forename: Shubeena
authors.initials: S
authors.lastname: Chib
authors.affiliation: From the Department of Biochemistry and Molecular Biology University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205.
authors.forename: Alicia K
authors.initials: AK
authors.lastname: Byrd
authors.affiliation: From the Department of Biochemistry and Molecular Biology University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205. Electronic address: raneykevind@uams.edu.
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Raney
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D004265:DNA Helicases / Q000378:metabolism*; D004271:DNA, Fungal / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D009693:Nucleic Acid Hybridization; D012331:RNA, Fungal / Q000737:chemistry / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D004271:DNA, Fungal; D012331:RNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; D000251:Adenosine Triphosphatases; C085463:PIF1 protein, S cerevisiae; D004265:DNA Helicases
keywords: DNA binding protein; DNA helicase; RNA; molecular motor; pre-steady state kinetics; yeast