Unnatural Cytosine Analogs Potentiate a Customizable, Enzymatic Method for Integrated Epigenetic and Four-Base Genetic Sequencing

The interplay of genetic and epigenetic information shapes cell identity, development, and disease. However, standard methods for profiling DNA modifications (e.g., bisulfite sequencing) rely on selective C-to-T conversions, hindering the simultaneous examination of both genetic and epigenetic information. Here, we introduce Integrated Sequencing, which provides high-fidelity mapping of DNA modifications while preserving the native four-base genetic code in single DNA molecules. Integrated-Seq leverages the synthesis of a tethered copy strand with unnatural cytosine analogs that resist enzymatic conversion, combined with a novel DNA deaminase-helicase fusion that drives selective C-to-T conversion of natural cytosines in the original template strand. We demonstrate that Integrated-Seq is compatible with customizable enzymatic readouts to parse 5-methylcytosine and 5-hydroxymethylcytosine, and that preservation of the original four-base genetic code markedly improved enrichment, facilitating analysis of targeted genomic regions. Integrated-Seq thus provides a platform for simultaneous genetic and epigenetic analyses, paving the way for deep insights into fundamental biology and next-generation diagnostics.