Unleashing a novel function of endonuclease G in mitochondrial genome instability
- Indian Institute of Science Bangalore, India
- Post Graduate Institute of Medical Education and Research, India
Abstract
Having its genome makes the mitochondrion a unique and semiautonomous organelle within cells. Mammalian mitochondrial DNA (mtDNA) is a double-stranded closed circular molecule of about 16 kb coding for 37 genes. Mutations, including deletions in the mitochondrial genome, can culminate in different human diseases. Mapping the deletion junctions suggests that the breakpoints are generally seen at hotspots. '9-bp deletion' (8271-8281), seen in the intergenic region of cytochrome c oxidase II/tRNALys, is the most common mitochondrial deletion. While it is associated with several diseases like myopathy, dystonia, and hepatocellular carcinoma, it has also been used as an evolutionary marker. However, the mechanism responsible for its fragility is unclear. In the current study, we show that Endonuclease G, a mitochondrial nuclease responsible for nonspecific cleavage of nuclear DNA during apoptosis, can induce breaks at sequences associated with '9-bp deletion' when it is present on a plasmid or in the mitochondrial genome. Through a series of in vitro and intracellular studies, we show that Endonuclease G binds to G-quadruplex structures formed at the hotspot and induces DNA breaks. Therefore, we uncover a new role for Endonuclease G in generating mtDNA deletions, which depends on the formation of G4 DNA within the mitochondrial genome. In summary, we identify a novel property of Endonuclease G, besides its role in apoptosis and the recently described elimination of paternal mitochondria during fertilisation.
Data availability
All data generated or analysed during this study are included in the manuscript and supporting files. Source data for each data is provided along with the figures
Article and author information
Author details
Sathees C Raghavan
Funding
Council of Scientific and Industrial Research, India (37(1692)/17/EMR-11)
- Sathees C Raghavan
Department of Atomic Energy, Government of India (21/01/2016-BRNS/35074)
- Sathees C Raghavan
Department of Biotechnology, Ministry of Science and Technology, India (BT/PR/3458/COE/34/33/2015)
- Sathees C Raghavan
IISc-DBT partnership programme (BT/PR27952-INF/22/212/2018)
- Sathees C Raghavan
Indian Institute of Science
- Sumedha Dahal
Indian Institute of Science
- Humaira Siddiqua
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the Indian National Law on animal care and use. All of the animals were handled according to approved institutional animal care and use committee protocols (CAF-SOP) of the Indian Institute of Science, Bangalore. The protocol was approved by the Committee on the Ethics of Animal Experiments of the Central Animal Facility (CAF/Ethics/526/2016).
Copyright
© 2022, Dahal et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Unleashing a novel function of endonuclease G in mitochondrial genome instability
eLife 11:e69916.
https://doi.org/10.7554/eLife.69916
Further reading
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Background:
It has been reported that loss of PCBP2 led to increased reactive oxygen species (ROS) production and accelerated cell aging. Knockdown of PCBP2 in HCT116 cells leads to significant downregulation of fibroblast growth factor 2 (FGF2). Here, we tried to elucidate the intrinsic factors and potential mechanisms of bone marrow mesenchymal stromal cells (BMSCs) aging from the interactions among PCBP2, ROS, and FGF2.
Methods:
Unlabeled quantitative proteomics were performed to show differentially expressed proteins in the replicative senescent human bone marrow mesenchymal stromal cells (RS-hBMSCs). ROS and FGF2 were detected in the loss-and-gain cell function experiments of PCBP2. The functional recovery experiments were performed to verify whether PCBP2 regulates cell function through ROS/FGF2-dependent ways.
Results:
PCBP2 expression was significantly lower in P10-hBMSCs. Knocking down the expression of PCBP2 inhibited the proliferation while accentuated the apoptosis and cell arrest of RS-hBMSCs. PCBP2 silence could increase the production of ROS. On the contrary, overexpression of PCBP2 increased the viability of both P3-hBMSCs and P10-hBMSCs significantly. Meanwhile, overexpression of PCBP2 led to significantly reduced expression of FGF2. Overexpression of FGF2 significantly offset the effect of PCBP2 overexpression in P10-hBMSCs, leading to decreased cell proliferation, increased apoptosis, and reduced G0/G1 phase ratio of the cells.
Conclusions:
This study initially elucidates that PCBP2 as an intrinsic aging factor regulates the replicative senescence of hBMSCs through the ROS-FGF2 signaling axis.
Funding:
This study was supported by the National Natural Science Foundation of China (82172474).
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