Biology subjects

O'Donnell, M. E.

Publications and source records attributed to O'Donnell, M. E..

2 recordsLinked to original sources

bioRxiv2018

Replisome preservation by a single-stranded DNA gate in the CMG helicase

The eukaryotic replicative helicase CMG is assembled at replication origins and is thought to remain topologically closed until termination. Upon encountering a lesion, CMG must vacate a stalled fork to allow DNA repair. However, the fate of CMG under these stress conditions remains unclear. Here, using correlative single-molecule fluorescence and force microscopy, we show that when uncoupled from a DNA polymerase, CMG opens a single-stranded (ss) DNA gate to traverse a forked junction and reside on double-stranded (ds) DNA. Surprisingly, CMG undergoes rapid diffusion on dsDNA and can transition back onto ssDNA for continued fork progression. The accessory protein Mcm10 is required for robust ssDNA gating. These results reveal an Mcm10-induced pathway that preserves CMG on DNA and allows it to access a repaired fork for swift replication recovery.

biophysics↗

bioRxiv2017

Mcm10 functions to isomerize CMG-DNA for replisome bypass of DNA blocks

Replicative helicases of all cell types are rings that unwind DNA by steric exclusion in which the helicase ring only encircles the tracking strand, excluding the other strand outside the ring. Steric exclusion mediated unwinding enables helicase rings to bypass blocks on the strand that is excluded from the central channel. Unlike other replicative helicases, eukaryotic CMG encircles duplex DNA at a forked junction and is stopped by a block on the non-tracking (lagging) strand. This report demonstrates that Mcm10, an essential replication protein unique to eukaryotes, binds CMG and enables the replisome to bypass blocks on the non-tracking strand, implying that Mcm10 isomerizes the CMG-DNA complex to position only one strand through the central channel. A similar CMG-DNA isomerization is needed at the origin for head-to-head CMGs to bypass one another during formation of bidirectional replication forks.

biochemistry↗