Figure 7: Mus81 endonuclease activity prevents irreversible fork stalling in response to perturbed replication. | Nature Communications

Figure 7: Mus81 endonuclease activity prevents irreversible fork stalling in response to perturbed replication.

From: The DNA repair endonuclease Mus81 facilitates fast DNA replication in the absence of exogenous damage

Figure 7

(a) Cells were labelled with IdU (green) for 10 min, then CldU (red) for 20 min. A low dose of APH was included during the CldU incubation period (left). Cells were harvested for single DNA fibre spread analysis. The right schematic graph showed three typical replication tracks: regular fork, slow fork and stalled fork based on the length of red replication tracks affected by APH treatment. (b) Images of DNA fibres from Mus81-proficient (HCT116) and Mus81-deficient (Mus81−/−) cells. Five representative fibres for each image were extracted and aligned to the right of their respective images. Effects of APH are shown in the bottom panels. Fibres that replicated with a similar pace during the IdU (green) and CldU (red) labelling periods exhibited a red signal that was longer than the green signal (regular fork), and most of replication forks in the control samples for both HCT116 and Mus81−/− cells belong to this category (2 top panels); fibres that slowed replication during the CldU labelling period exhibited a red signal that was clearly shorter than the green signal (slow fork), and most of replication forks in APH-treated HCT116 cells belong to this category (bottom left panel); and fibres that could not recover from replication inhibition exhibited green signals and no red signals (stalled), and most of replication forks in APH-treated Mus81−/− cells belong to this category (bottom right panel). (c) Images of DNA fibres from Mus81-deficient cells that express wild-type Mus81 (Mus81−/− com-wt Mus81) or mutant Mus81 (Mus81−/−comp-mutt Mus81). Mutant Mus81 lacks endonuclease activity. Effects of APH are shown in the bottom panels. Five representative fibres from APH-treated wild-type Mus81 and mutant Mus81 samples (Fig. 7c, two bottom panels) were selected and aligned under their original images, respectively. Most of wild-type Mus81 cells showed slow forks while most of mutant-type Mus81 cells showed stalled forks after low dose of APH treatment.

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