Pif1 Helicase Directs Eukaryotic Okazaki Fragments toward the Two-nuclease Cleavage Pathway for Primer Removal

摘要: Eukaryotic Okazaki fragment maturation requires complete removal of the initiating RNA primer before ligation occurs. Polymerase δ (Pol δ) extends upstream and displaces 5′-end downstream into a single nucleotide flap, which is removed by FEN1 nuclease cleavage. This process repeated until all removed. However, small fraction flaps escapes cleavage grows long enough to be coated with RPA consecutive action Dna2 nucleases for processing. Here we tested whether inhibits as proposed. Surprisingly, determined that binding made dynamically polymerase only slightly inhibited cleavage, apparently obviating need Dna2. Therefore, asked other relevant proteins promote flap via pathway. The Pif1 helicase, implicated in from genetic studies, improved displacement increased inhibition FEN1. These results suggest accelerates growth, allowing bind can act, thereby inhibiting directs toward two-nuclease pathway, requiring removal.