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. 2020 Oct;594(19):3142-3155.
doi: 10.1002/1873-3468.13893. Epub 2020 Aug 9.

Irc3 is a monomeric DNA branch point-binding helicase in mitochondria of the yeast Saccharomyces cerevisiae

Vlad-Julian Piljukov  1 , Natalja Garber  1 , Tiina Sedman  1 , Juhan Sedman  1
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Free article

Irc3 is a monomeric DNA branch point-binding helicase in mitochondria of the yeast Saccharomyces cerevisiae

Vlad-Julian Piljukov et al. FEBS Lett. 2020 Oct.
Free article

Abstract

Irc3 is a superfamily II DNA helicase required for the maintenance of mitochondrial DNA stability in Saccharomyces cerevisiae. Here, we show that recombinant Irc3 is a monomeric protein and that it can form a binary complex with forked DNA. The catalytically active enzyme is a monomer as no positive cooperativity of ATP hydrolysis or DNA unwinding can be detected. Interestingly, we find that Irc3 prefers to unwind the nascent lagging strand at a replication fork. Using DNase I footprinting, we demonstrate that Irc3 captures DNA substrates by establishing a strong contact at the DNA branching point. Additional protections on the lagging strand template suggest a 3'-to-5' polarity for Irc3 movement.

Keywords: DNA branch point; DNA helicase; mitochondria; yeast.

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