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Review
. 2025 May 16;11(20):eadx6879.
doi: 10.1126/sciadv.adx6879. Epub 2025 May 14.

Introducing the "other" type of DNA methylation

Matthias Bochtler  1   2
Affiliations
Review

Introducing the "other" type of DNA methylation

Matthias Bochtler. Sci Adv. .

Abstract

De novo adenine DNA methyltransferases have been identified in the ciliate Tetrahymena.

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Figures

Fig. 1.
Fig. 1.. Adenine DNA methylation in Tetrahymena.
(A) De novo methylation introduces methyl groups (blue) into otherwise nonmethylated DNA. ApT describes the methylation context, which is the palindromic adenine-thymine sequence. (B) Maintenance methylation converts hemimethylation back to full methylation (i.e., methylation of both DNA strands) after DNA replication. (C) Ciliates such as Tetrahymena have two nuclei, a micronucleus (MIC, orange) and a macronucleus (MAC, red). (D) De novo methylation in Tetrahymena occurs when a descendant of the MIC (orange) matures to the MAC (red) during sexual reproduction. It is catalyzed by AMT2/AMT5. Once established, methylation in the MAC is preserved by the maintenance methyltransferases AMT1/AMT6 and AMT1/AMT7 during asexual reproduction. Illustration credit: Austin Fisher/Science Advances.
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