Archaeal replicative primase mediates DNA double-strand break repair

Area of Science:

• Molecular Biology
• Genetics
• Extremophile Biology

Background:

• Archaea inhabit extreme environments and possess robust DNA repair mechanisms.
• DNA double-strand breaks (DSBs) are highly lethal DNA lesions, and their repair in Archaea is not well understood.

Purpose of the Study:

• To investigate the role of replicative primase in DNA double-strand break (DSB) repair in the hyperthermophilic archaeon Saccharolobus islandicus.

Main Methods:

• Investigated the effect of overproducing or knocking down the PriL subunit of replicative primase on cell survival and mutation frequency after DNA damage.
• Assessed the repair of CRISPR-generated DSBs in vivo with varying levels of PriL.
• Examined the cell-cycle dependency of primase-mediated DSB repair.

Main Results:

• Overproduction of PriL enhanced survival and DSB repair, while knockdown decreased survival and increased mutation frequency (small insertions/deletions).
• Replicative primase (PriSL) exhibits microhomology-dependent DNA strand annealing activity.
• Primase-mediated DSB repair is cell-cycle dependent, with PriL levels low during S/G2 transition.

Conclusions:

• Replicative primase plays a significant role in DNA double-strand break repair in Archaea.
• The mechanism involves microhomology-mediated end joining (MMEJ).
• This finding highlights a novel function for primase beyond its canonical role in DNA replication initiation.