Oxidative stress preferentially induces a subtype of micronuclei and mediates the genomic instability caused by p53
Abstract:
Reactive oxygen species (ROS) are known to cause many types of DNA lesions that could be converted into cancer-promoting genetic alterations. Evidence showed that tumor suppressor p53 plays an important role in regulating the generation of cellular ROS, either by reducing oxidative stress under physiological and mildly stressed conditions, or by promoting oxidative stress under highly stressed conditions. In this report we characterized the effect of oxidative stress on the induction of micronuclei, especially the subclass marked by pan-staining of γ-H2AX or MN-γ-H2AX (+). We found that MN-γ-H2AX (+) were more responsive to hydrogen peroxide (H2O2) than the MN-γ-H2AX (−). In human and mouse cells that are deficient in p53, the frequency of MN-γ-H2AX (+) is significantly elevated, but can be attenuated by antioxidant N-acetylcysteine (NAC). Depletion of p53-regulated antioxidant gene SESN1 by RNA interference also resulted in an elevation of MN-γ-H2AX (+). Furthermore, we found that in cells that were depleted of p400 by RNAi, and therefore were experiencing increased ROS, the frequency of MN-γ-H2AX (+), but not that of MN-γ-H2AX (−), was significantly induced. We further demonstrated that the induction of MN-γ-H2AX (+) by replication stress can also be attenuated by NAC, and that H2O2 also leads to increased phosphorylation of Chk1 and Rad17 that mimics replication stress, suggesting that replication stress and oxidative stress are intertwined and may reinforce each other in driving genomic instability. Our findings illustrate the importance of p53-regulated redox level in the maintenance of genomic stability.
Insights
The tumor suppressor p53 regulates cellular reactive oxygen species (ROS) to maintain genomic stability. Loss of p53 increases ROS-induced DNA damage, specifically micronuclei marked by γ-H2AX, highlighting p53
Area of Science:
- Genetics
- Molecular Biology
- Cellular Biology
Background:
- Reactive oxygen species (ROS) induce DNA lesions, potentially leading to cancer.
- The tumor suppressor p53 influences cellular ROS levels, acting as an antioxidant or pro-oxidant depending on stress conditions.
- Micronuclei formation is a marker of genomic instability.
Purpose of the Study:
- To investigate the role of p53 in regulating oxidative stress-induced DNA damage, focusing on micronuclei formation.
- To characterize the subclass of micronuclei marked by γ-H2AX (MN-γ-H2AX (+)) and their response to oxidative stress.
- To explore the interplay between p53, ROS, and genomic instability.
Main Methods:
- Utilizing human and mouse cell lines with and without p53.
- Employing hydrogen peroxide (H2O2) to induce oxidative stress.
- Using RNA interference (RNAi) to deplete specific genes (SESN1, p400).
- Assessing micronuclei formation and γ-H2AX staining.
- Treating cells with N-acetylcysteine (NAC) as an antioxidant.
- Analyzing Chk1 and Rad17 phosphorylation.
Main Results:
- MN-γ-H2AX (+) were more sensitive to H2O2 than MN-γ-H2AX (−).
- p53-deficient cells showed elevated MN-γ-H2AX (+), which was reduced by NAC.
- Depletion of SESN1, a p53-regulated gene, increased MN-γ-H2AX (+).
- Depletion of p400, leading to increased ROS, also elevated MN-γ-H2AX (+).
- Replication stress-induced MN-γ-H2AX (+) was attenuated by NAC.
- H2O2 induced markers of replication stress (Chk1, Rad17 phosphorylation).
Conclusions:
- p53 plays a crucial role in maintaining genomic stability by regulating cellular redox levels.
- Oxidative stress and replication stress are interconnected and can mutually reinforce genomic instability.
- Targeting p53-mediated redox regulation may offer strategies for preventing cancer-promoting genetic alterations.
Related Concept Videos
02:23Abnormal Proliferation
02:36DNA Damage can Stall the Cell Cycle
02:36DNA Damage Can Stall the Cell Cycle
01:38Nucleotide Excision Repair
Cells are regularly exposed to mutagens—factors in the environment that can damage DNA and generate mutations. UV radiation is one of the most common mutagens and is estimated to introduce a significant number of changes in DNA. These include bends or kinks in the structure, which can block DNA replication or transcription. If these errors are not fixed, the damage can cause mutations, which in turn can result in cancer or disease depending on which sequences are...
01:08Nucleotide Excision Repair
01:30Spontaneous and Induced Mutations