PubMed · 7862537
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S Belikov, L Wieslander. 1995-01-25. Express protocol for generating G+A sequencing ladders.. https://doi.org/10.1093/nar%2F23.2.310
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DNA N6-methyladenine (6mA) is a newly recognized transcription-associated epigenetic mark in eukaryotes. While its methylation pathway has been well established, the identity of eukaryotic 6mA demethylase(s) responsible for its removal and dynamic regulation has remained elusive. Here, we identify and characterize DMT3 (TtALKBH5), an AlkB family dioxygenase in Tetrahymena thermophila, as a 6mA demethylase in ciliates and potentially several other unicellular eukaryotes with abundant 6mA and a defined AMT1 methyltransferase (MTase) complex, supported by genetic and molecular evidence. DMT3 acts on both fully and hemimethylated ApT dinucleotides, an activity partially facilitated by a naturally occurring cysteine-to-serine substitution. Genome profiling shows that DMT3 is enriched at transcription start sites (TSSs) of 6mA-enriched genes, complementary to the occupancy pattern of the AMT1 complex, where it selectively removes spurious 6mA deposited by AMT1. Genetic disruption of DMT3-mediated demethylation, either by knockout or catalytic inactivation, leads to aberrant 6mA accumulation at TSS regions, transcriptional dysregulation, altered chromatin accessibility, and impaired initiation of sexual reproduction. Notably, simultaneous removal of DMT3 and AMT1 eliminates these defects, indicating that spurious TSS 6mA underlies transcriptional and developmental impairment.
A strategy coupling high-activity nucleases with dimeric TadA-8e optimizes plant Cas12-based adenine base editors, boosts editing efficiency, and provides precise editors for crop breeding and genomics research.
The ribosome-inactivating proteins (RIPs) from Hura crepitans and Phytolacca americana release adenine from herring sperm DNA. Leaf extracts from these plants show the same enzymatic activities as the RIPs. The translation inhibitory activity and the activity on DNA are both increased in the leaves of both plants during senescence or when subjected to heat or osmotic stress. It is proposed that a physiological role of RIPs could be to intervene in the death of plant cells.