DNA N6-methyldeoxyadenosine in mammals and human disease

6mA is an abundant and functionally important modification in prokaryotes. Recently, emerging evidence supports its presence in eukaryotes, including mammals. In mammals, 6mA level is consistently low in normal mouse tissues, but varies in human cell lines or tissues. In addition, 6mA abundance is dynamic during normal development and disease progression. The genomic distribution of 6mA and its roles in gene regulation are tissue/biological process-dependent. Common features, distinct findings, and research limitations are discussed. Several proteins have been reported to function as 6mA writers or erasers in mammals, but some require further confirmation. Dysregulated 6mA levels and its regulators contribute to the development of human diseases including cancers. Targeting 6mA and its regulators holds potential in cancer treatment. N6-methyladenine (6mA) is the most prevalent DNA modification in prokaryotes. However, its presence and significance in eukaryotes remain elusive. Recently, with methodology advances in detection and sequencing of 6mA in eukaryotes, 6mA is back in the spotlight. Although multiple studies have reported that 6mA is an important epigenetic mark in eukaryotes and plays a regulatory role in DNA transcription, transposon activation, stress response, and other bioprocesses, there are some discrepancies in the current literature. We review the recent advances in 6mA research in eukaryotes, especially in mammals. In particular, we describe the abundance/distribution of 6mA, its potential role in regulating gene expression, identified regulators, and pathological roles in human diseases, especially in cancer. The limitations faced by the field and future perspectives in 6mA research are also discussed. N6-methyladenine (6mA) is the most prevalent DNA modification in prokaryotes. However, its presence and significance in eukaryotes remain elusive. Recently, with methodology advances in detection and sequencing of 6mA in eukaryotes, 6mA is back in the spotlight. Although multiple studies have reported that 6mA is an important epigenetic mark in eukaryotes and plays a regulatory role in DNA transcription, transposon activation, stress response, and other bioprocesses, there are some discrepancies in the current literature. We review the recent advances in 6mA research in eukaryotes, especially in mammals. In particular, we describe the abundance/distribution of 6mA, its potential role in regulating gene expression, identified regulators, and pathological roles in human diseases, especially in cancer. The limitations faced by the field and future perspectives in 6mA research are also discussed. a method for identifying N6-methyladenine (6mA) sites at the whole-genome level. Anti-6mA antibodies are first crosslinked onto 6mA-containing double-stranded (ds)DNA fragments, which are thus protected from subsequent 5′-to-3′ exonuclease treatment. Exonuclease degradation of all genomic DNA other than regions proximal to the protected 6mA is then performed before sequencing. a technique that uses antibody binding and NGS to measure the genome-wide enrichment of a specific DNA modification. long interspersed nuclear element (LINE) transposable elements in the DNA of some organisms. Active class 1 (L1) LINE elements can interrupt the genome through insertions, deletions, rearrangements, and copy-number variations (CNVs). L1 elements are tightly regulated in the germline by DNA methylation, histone modifications, and Piwi-interacting RNA (piRNA). a technique that performs sequencing of millions of small fragments of DNA in parallel. Bioinformatic analyses are used to piece together these fragments by mapping the individual reads to the reference genome. a non-canonical nucleic acid structure that forms when nascent transcripts anneal to the DNA template strand or any homologous DNA region. Improper turnover and/or unscheduled formation can lead to DNA damage and genome instability. a method for robust amplification of an entire genome. Because the amplicon generated by WGA does not contain any DNA modifications, it can be used as a negative control for studies of genome-wide distribution of a specific DNA modification by techniques such as DIP-seq.