Distinct roles of XRCC1 in genome integrity in Xenopus egg extracts.

Oxidative DNA damage represents one of the most abundant DNA lesions. It remains unclear how DNA repair and DNA damage response (DDR) pathways are co-ordinated and regulated following oxidative stress. While XRCC1 has been implicated in DNA repair, it remains unknown how exactly oxidative DNA damage is repaired and sensed by XRCC1.

APE2 promotes DNA damage response pathway from a single-strand break.

As the most common type of DNA damage, DNA single-strand breaks (SSBs) are primarily repaired by the SSB repair mechanism. If not repaired properly or promptly, unrepaired SSBs lead to genome stability and have been implicated in cancer and neurodegenerative diseases. However, it remains unknown how unrepaired SSBs are recognized by DNA damage response (DDR) pathway, largely because of the lack of a feasible experimental system.

Cell-free Xenopus egg extracts for studying DNA damage response pathways.

In response to a variety of DNA replication stress or DNA damaging agents, the DNA damage response (DDR) pathways are triggered for cells to coordinate DNA repair, cell cycle checkpoints, apoptosis, and senescence. Cell-free Xenopus egg extracts, derived from the eggs of African clawed frogs (Xenopus laevis), have been widely used for studies concerning DDR pathways. In this review, we focus on how different experimental systems have been established using Xenopus egg extracts to investigate the DDR pathways that are activated in response to DNA replication stress, double-strand breaks (DSBs), inter-strand crosslinks (ICLs), and oxidative stress.