Cytosine residue (None; commonly referred to as "C" in nucleic acid sequences, but "cytosine residue" does not have a standard scientific abbreviation.)

Cytosine residue refers to the individual cytosine base as it occurs covalently bound within a nucleic acid polymer (DNA or RNA). Cytosine is one of the four standard nucleobases in DNA and RNA, classified as a pyrimidine, and is denoted by the letter "C"[1][5]. It pairs with guanine via three hydrogen bonds. Cytosine residues can be post-transcriptionally modified, such as by methylation to form 5-methylcytosine—a key epigenetic control mechanism regulating gene expression and cellular identity[2][4][8]. Deamination, oxidation, or other chemical changes to cytosine residues can have profound consequences, including mutagenesis (conversion to uracil), immune diversity, and disease association, particularly in cancer where DNA methylation patterns are often disrupted[2][4][8]. The cytosine residue itself is not a receptor, enzyme, transporter, or therapeutic target. Instead, it is a chemical component of nucleic acids and a substrate for various modifying enzymes (such as DNA methyltransferases or cytosine deaminases)[2][4][8]. Cytosine modifications, particularly 5-methylcytosine, serve as established epigenetic biomarkers for diseases such as cancer[7][8]. Important caveat: "Cytosine residue" is not a drug target; it is a chemical moiety within nucleic acids. If you intended a druggable protein or nucleic acid (like a methyl-CpG binding protein or DNA methyltransferase), please specify that target. Cytosine analogs (e.g., cytarabine) are used as drugs, but these act as nucleotide analogs; the cytosine residue itself is not therapeutically targeted.

Other names

CytosineC4-Amino-2-hydroxypyrimidineCytosinimine4-aminopyrimidin-2(1H)-one[5]

Not applicable (Cytosine residue is a chemical moiety within nucleic acids, not a protein or nucleic acid target with specific drug mechanisms)