Pif1 is essential for efficient replisome progression through lagging strand G-quadruplex DNA secondary structures

Danielle Dahan, Ioannis Tsirkas, Daniel Dovrat, Melanie A Sparks, Saurabh P Singh, Roberto Galletto, Amir Aharoni
2018 Nucleic Acids Research  
Pif1 DNA helicase is a potent unwinder of Gquadruplex (G4) structures in vitro and functions to maintain genome stability at G4 sequences in Saccharomyces cerevisiae. Here, we developed and utilized a live-cell imaging approach to quantitatively measure the progression rates of single replication forks through different G4 containing sequences in individual yeast cells. We show that in the absence of Pif1, replication rates through specific lagging strand G4 sequences in vivo is significantly
more » ... is significantly decreased. In contrast, we found that in the absence of Pif1, replication rates through the same G4s on the leading strand are not decreased relative to the respective WT strains, showing that Pif1 is essential only for efficient replication through lagging strand G4s. Additionally, we show that a canonical PIP sequence in Pif1 interacts with PCNA and that replication through G4 structures is significantly slower in the absence of this interaction in vitro and in vivo. Thus, Pif1-PCNA interaction is essential for optimal replisome progression through G4 sequences, highlighting the importance of coupling between Pif1 activity and replisome progression during yeast genome replication.
doi:10.1093/nar/gky1065 pmid:30395308 fatcat:u3cxaqrfmze77nrlb3zlu7towy