Replication stress is defined as the events that take place when the genome is exposed to various stresses. It typically occurs during DNA replication, and can result in a stalled replication fork. ATM and ATR are proteins that mediate replication stress. Specifically, they are kinases that are recruited and activated by DNA damage. The stalled replication fork can collapse if these regulatory proteins fail to stabilize it. When this occurs, reassembly of the fork is initiated in order to repair the damaged DNA end.
The replication fork consists of a group of proteins that influence the activity of DNA replication. In order for the replication fork to stall, the cell must possess a certain number of stalled forks and arrest length. The replication fork is specifically paused due to the stalling of helicase and polymerase activity, which are linked together. In this situation, the fork protection complex (FPC) is recruited to help maintain this linkage.
In addition to stalling and maintaining the fork structure, protein phosphorylation can also create a signal cascade for replication restart. The protein Mrc1, which is part of the FPC, transmits the checkpoint signal by interacting with kinases throughout the cascade. When there is a loss of these kinases (from replication stress), an excess of ssDNA is produced, which is necessary for the restarting of replication.
Replication block removal
DNA interstrand cross-links (ICLs) cause replicative stress by blocking replicative fork progression. This blockage leads to failure of DNA strand separation and a stalled replication fork. Repair of ICLs can be accomplished by sequential incisions, and homologous recombination. In vertebrate cells, replication of an ICL-containing chromatin template triggers recruitment of more than 90 DNA repair and genome maintenance factors. Analysis of the proteins recruited to stalled replication forks revealed a specific set of DNA repair factors involved in the replication stress response. Among these proteins, SLF1 and SLF2 were found to physically link the SMC5/6 DNA repair protein complex to RAD18. The SMC5/6 complex is employed in homologous recombination, and its linkage to RAD18 likely allows recruitment of SMC5/6 to ubiquitination products at sites of DNA damage.
Replication stress is induced from various endogenous and exogenous stresses, which are regularly introduced to the genome. These stresses include, but are not limited to, DNA damage, excessive compacting of chromatin (preventing replisome access), over-expression of oncogenes, or difficult-to-replicate genome structures. Replication stress can lead to genome instability, cancer, and ageing. Uncoordinated replication–transcription conflicts and unscheduled R-loop accumulation are significant contributors.
The events that lead to genome instability occur in the cell cycle prior to mitosis, specifically in the S phase. Disturbance to this phase can generate negative effects, such as inaccurate chromosomal segregation, for the upcoming mitotic phase. The two processes that are responsible for damage to the S phase are oncogenic activation and tumor suppressor inactivation. They have both been shown to speed up the transition from the G1 phase to the S phase, leading to inadequate amounts of DNA replicative components. These losses can contribute to the DNA damage response (DDR). Replication stress can be an indicative characteristic for carcinogenesis, which typically lacks DNA repair systems. A physiologically short duration of the G1 phase is also typical of fast replicating progenitors during early embryonic development.
Applications in cancer
Although replication stress has been linked to carcinogenesis, studies have been conducted which show that replication stress could be used as a treatment for cancer. One specific study examined how replication stress affected APOBEC3B activity. APOBEC3 (apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3) has been seen to mutate the cancer genome in various cancer types. Results from this study show that weakening oncogenic signaling or intensifying DNA replication stress can alter carcinogenic potential, and can be manipulated therapeutically.
Normal replicative stress occurs at low to mild levels and induces genomic instability, which can lead to tumorigenesis and cancer progression. Researchers decided to conduct a study to determine the effects of inducing high levels of replicative stress on cancer cells. The results showed that with further loss of checkpoints, replicative stress is increased to a higher level. With this change, the DNA replication of cancer cells may be incomplete or incorrect when entering into the mitotic phase. This can eventually result in cell death through mitotic catastrophe.
- Mazouzi A, Velimezi G, Loizou JI (2014). "DNA replication stress: causes, resolution and disease". Experimental Cell Research. 329 (1): 85–93. doi:10.1016/j.yexcr.2014.09.030. PMID 25281304.
- "Reactome | Activation of ATR in response to replication stress". www.reactome.org. Retrieved 2017-04-09.
- Zeman MK, Cimprich KA (2014). "Causes and consequences of replication stress". Nature Cell Biology. 16 (1): 2–9. doi:10.1038/ncb2897. PMC 4354890. PMID 24366029.
- Allen, C.; Ashley, A. K.; Hromas, R.; Nickoloff, J. A. (2011-02-01). "More forks on the road to replication stress recovery". Journal of Molecular Cell Biology. 3 (1): 4–12. doi:10.1093/jmcb/mjq049. ISSN 1674-2788. PMC 3030971. PMID 21278446.
- "Replication Fork, Fork Protection Complex | Learn Science at Scitable". www.nature.com. Retrieved 2017-04-09.
- "Stalled DNA Replication Fork | Learn Science at Scitable". www.nature.com. Retrieved 2017-04-09.
- Räschle M, Smeenk G, Hansen RK, Temu T, Oka Y, Hein MY, Nagaraj N, Long DT, Walter JC, Hofmann K, Storchova Z, Cox J, Bekker-Jensen S, Mailand N, Mann M (2015). "DNA repair. Proteomics reveals dynamic assembly of repair complexes during bypass of DNA cross-links". Science. 348 (6234): 1253671. doi:10.1126/science.1253671. PMC 5331883. PMID 25931565.
- "Replication Stress in Mammalian Cells and Its Consequences for Mitosis (PDF Download Available)". ResearchGate. Retrieved 2017-02-11.
- Burhans WC1, Weinberger M (2007). "DNA replication stress, genome instability and aging". Nucleic Acids Research. 35 (22): 7545–7556. doi:10.1093/NAR/GKM1059. PMC 2190710. PMID 18055498.
- Fragkos, Michalis; Naim, Valeria (2017-04-03). "Rescue from replication stress during mitosis". Cell Cycle (Georgetown, Tex.). 16 (7): 613–633. doi:10.1080/15384101.2017.1288322. ISSN 1551-4005. PMC 5397263. PMID 28166452.
- Brambati, Alessandra; Colosio, Arianna; Zardoni, Luca; Galanti, Lorenzo; Liberi, Giordano (2015-04-28). "Replication and transcription on a collision course: eukaryotic regulation mechanisms and implications for DNA stability". Frontiers in Genetics. 6: 166. doi:10.3389/fgene.2015.00166. ISSN 1664-8021. PMC 4412130. PMID 25972894.
- Zhang, Jun; Dai, Qun; Park, Dongkyoo; Deng, Xingming (2016-08-19). "Targeting DNA Replication Stress for Cancer Therapy". Genes. 7 (8): 51. doi:10.3390/genes7080051. PMC 4999839. PMID 27548226.
- Cescon, David W.; Haibe-Kains, Benjamin (2016-01-01). "DNA replication stress: a source of APOBEC3B expression in breast cancer". Genome Biology. 17 (1): 202. doi:10.1186/s13059-016-1069-y. ISSN 1474-760X. PMC 5045630. PMID 27716362.
- Takahashi, T; Nowakowski, RS; Caviness, VS Jr. (1995-01-01). "The cell cycle of the pseudostratified ventricular epithelium of the embryonic murine cerebral wall". J. Neurosci. 15 (9): 6046–57. doi:10.1523/JNEUROSCI.15-09-06046.1995. PMID 666188.
- Kanu, Nnennaya; Cerone, Maria Antonietta; Goh, Gerald; Zalmas, Lykourgos-Panagiotis; Bartkova, Jirina; Dietzen, Michelle; McGranahan, Nicholas; Rogers, Rebecca; Law, Emily K. (2016-01-01). "DNA replication stress mediates APOBEC3 family mutagenesis in breast cancer". Genome Biology. 17 (1): 185. doi:10.1186/s13059-016-1042-9. ISSN 1474-760X. PMC 5025597. PMID 27634334.
- Taylor, Elaine M; Lindsay, Howard D (2015-11-30). "DNA replication stress and cancer: cause or cure?". Future Oncology. 12 (2): 221–237. doi:10.2217/fon.15.292. ISSN 1479-6694. PMID 26616915.