Abstract: The disclosure provides methods and related kits, reagents, and systems for selectively deaminating unmethylated cytosine residues in nucleic acid molecules. In some embodiments, the methods and related kits, reagents, and systems are applied for methods of detecting and/or mapping methylated cytosine residues in nucleic acids. The nucleic can be RNA or DNA. Some embodiments include contacting the polynucleic acid with a bacterial cytosine deaminase, for example DddA or SsdA, or functional fragments or derivatives thereof. Representative DddA and SsdA have sequences set forth in SEQ ID NOS:1 and 2, respectively. The bacterial cytosine deaminases of the disclosure are sensitive to methylation and, thus, deaminate only unmethylated cytosines to provide a cytosine to uracil conversion. The conversion can be detected as a C•G-to-T•A transitions in subsequent sequencing analysis.

Abstract: The disclosure provides methods and related compositions and kits for mapping DNA-protein interactions (DPIs). In one aspect, the disclosed methods comprise contacting a double stranded DNA molecule with a target protein; coupling a double stranded DNA deaminase (DddA) to the target protein, before or after the contacting step; permitting deamination of one or more cytosine residues in a domain of the double stranded DNA molecule by the DddA to provide one or more uracil residues, wherein the domain comprises a site of interaction between the target protein and the double stranded DNA molecule; determining the sequence of at least a portion of the double stranded DNA molecule; and detecting the domain comprising one or more cytosine deamination events. The method can be controlled by use of DddA inhibitors. The method can also incorporate use of inhibiting a base-excision repair pathway when addressing DPIs in a cellular context.