ssDNA-seq mapping of DNA secondary structures in mouse ES cells

DNA N6-methyladenine (N6-mA) is an emerging epigenetic mark in the mammalian genome. Levels of N6-mA undergo drastic fluctuation during early embryogenesis, indicative of active regulation. Here we demonstrate that the 2-oxoglurarate oxygenase ALKBH1 functions as a nuclear eraser of N6-mA in unpairing regions (e.g. SIDD, Stress Induced DNA Double Helix Destabilization regions). Enzymatic profiling studies revealed that ALKBH1 displays demethylation activity towards N6-mA on DNA substrates that share a common unpairing feature, e.g. bubbled, bulged or single-stranded DNA oligos. Furthermore, ssDNA-seq and DIP-seq analyses revealed significant genome-wide co-occurrence of base unpairing regions with N6-mA in mouse embryonic stem cells, especially during cell fate transition. Collectively, our biochemical, structural and genomic studies demonstrate that ALKBH1 is an important DNA demethylase that regulates genome N6-mA turnover in unpairing regions associated with dynamic chromatin regulation in early development. This series contains data from ssDNA-seq experiments on mouse ES cells. We used the S1 nuclease and biotin end-labeling to enrich for DNA at ssDNA regions followed by HiSeq4000 sequencing and data analysis. Overall design: Genomic DNA pulldown with HiSeq sequencing