RAD18 Is a Maternal Limiting Factor Silencing the UV-Dependent DNA Damage Checkpoint in Xenopus Embryos

Abstract

In early embryos, the DNA damage checkpoint is silent until the midblastula transition (MBT) because of maternal limiting factors of unknown identity. Here we identify the RAD18 ubiquitin ligase as one such factor in Xenopus. We show, in vitro and in vivo, that inactivation of RAD18 function leads to DNA damage-dependent checkpoint activation, monitored by CHK1 phosphorylation. Moreover, we show that the abundance of both RAD18 and PCNA monoubiquitylated (mUb) are developmentally regulated. Increased DNA abundance limits the availability of RAD18 close to the MBT, thereby reducing PCNA(mUb) and inducing checkpoint derepression. Furthermore, we show that this embryonic-like regulation can be reactivated in somatic mammalian cells by ectopic RAD18 expression, therefore conferring resistance to DNA damage. Finally, we find high RAD18 expression in cancer stem cells highly resistant to DNA damage. Together, these data propose RAD18 as a critical embryonic checkpoint-inhibiting factor and suggest that RAD18 deregulation may have unexpected oncogenic potential.

RAD18 may function as a predictor of response to preoperative concurrent chemoradiotherapy in patients with locally advanced rectal cancer through caspase‐9‐caspase‐3‐dependent apoptotic pathway

“…Many previous studies have revealed that abnormal expression of RAD18 could be found in different cancer cells . High RAD18 expression enhances translesion synthesis and double‐strand breaks repair, leading to tolerance of DNA damage and replication stress, thus resulting in chemo‐resistance . High RAD18 level in cancer cells also represents extreme resistance to IR by regulating DNA damage‐dependent checkpoint and G2/M checkpoint .…”

Zygotic Genome Activation in Vertebrates

“…At the 12 th division, the cell cycle slows when S-phase lengthens, divisions of neighboring cells become asynchronous, and cells become motile (Iwao et al, 2005; Newport and Kirschner, 1982a). Concurrently, replication and DNA damage checkpoints are activated, and G1 and G2 phases emerge (Anderson et al, 1997; Kermi et al, 2015; Masui and Wang, 1998). In both species, the initial cell cycle lengthening coincides with a significant increase in zygotic transcription, but does not necessarily depend on zygotic transcription.…”

Using Xenopus to understand human disease and developmental disorders

“…While it has been an outstanding system in which to make fundamental discoveries, Xenopus has also played a major role in understanding pathological processes. For example, Xenopus has been used to advance our understanding of DNA damage response and apoptosis (Kermi et al, ; McCoy et al, ; Olivera Harris et al, ; Shi et al, ; Tammaro, Liao, Beeharry, & Yan, ), immune and inflammatory responses (Edholm, Grayfer, De Jesús Andino, & Robert, ; Grayfer & Robert, 2014; Haynes‐Gilmore et al, ; Paredes, Ishibashi, Borrill, Robert, & Amaya, ; Wangkanont, Wesener, Vidani, Kiessling, & Forest, ), regenerative plasticity and wound healing (Franchini & Bertolotti, ; Hayashi et al, ; Muñoz et al, ; Wang & Beck, ; Wang, Keenan, Lynn, McEwan, & Beck, ), and responses to environmental toxicity (Chen, Wang, Zhu, Ding, & Peng, ; Hellyer et al, ; Sai et al, ). In addition, it has been used to great advantage in the development of therapeutics (e.g., Quadri, Papke, & Horenstein, ; Rodrigues et al, ; Volkman et al, 2016).…”