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Updated: May 17, 2025

A Method for Measuring RNA N6-methyladenosine Modifications in Cells and Tissues
Published on: December 5, 2016
N6-methyladenosine in DNA promotes genome stability
Brooke A Conti1, Leo Novikov1, Deyan Tong2
1Centers for Therapeutic Innovation, Emerging Sciences and Innovation, Pfizer, New York, United States.
Abstract:
DNA base lesions, such as incorporation of uracil into DNA or base mismatches, can be mutagenic and toxic to replicating cells. To discover factors in repair of genomic uracil, we performed a CRISPR knockout screen in the presence of floxuridine, a chemotherapeutic agent that incorporates uracil and fluorouracil into DNA. We identified known factors, such as uracil DNA N-glycosylase (UNG), and unknown factors, such as the N6-adenosine methyltransferase, METTL3, as required to overcome floxuridine-driven cytotoxicity. Visualized with immunofluorescence, the product of METTL3 activity, N6-methyladenosine, formed nuclear foci in cells treated with floxuridine. The observed N6-methyladenosine was embedded in DNA, called 6mA, and these results were confirmed using an orthogonal approach, liquid chromatography coupled to tandem mass spectrometry. METTL3 and 6mA were required for repair of lesions driven by additional base-damaging agents, including raltitrexed, gemcitabine, and hydroxyurea. Our results establish a role for METTL3 and 6mA in promoting genome stability in mammalian cells, especially in response to base damage.
Insights
Researchers discovered that METTL3 and its product 6mA are crucial for repairing DNA damage caused by agents like floxuridine. This finding highlights their role in maintaining genome stability in mammalian cells.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- DNA base lesions, including uracil incorporation and mismatches, pose risks to cellular replication and genome integrity.
- Chemotherapeutic agents like floxuridine can introduce uracil into DNA, leading to cytotoxicity.
Purpose of the Study:
- To identify factors involved in the repair of genomic uracil lesions.
- To investigate the role of METTL3 and its product 6mA in DNA damage response.
Main Methods:
- Conducted a CRISPR knockout screen using floxuridine to identify essential repair factors.
- Utilized immunofluorescence to visualize N6-methyladenosine (6mA) foci.
- Employed liquid chromatography-tandem mass spectrometry for orthogonal confirmation of 6mA in DNA.
Main Results:
- Identified known (UNG) and novel factors, including METTL3, essential for overcoming floxuridine-induced cytotoxicity.
- Observed nuclear foci of 6mA in floxuridine-treated cells, confirming its presence in DNA.
- Demonstrated that METTL3 and 6mA are required for repairing lesions induced by various DNA-damaging agents (raltitrexed, gemcitabine, hydroxyurea).
Conclusions:
- Established a significant role for METTL3 and DNA 6mA in promoting mammalian genome stability.
- Highlighted the importance of the METTL3-6mA pathway in cellular response to base damage.
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