Uracilation

Uracilation is a biological process that involves the incorporation of uracil into nucleic acids. Uracil is one of the four nucleotide bases found in RNA, where it pairs with adenine. In DNA, uracil is normally absent and is replaced by thymine. The presence of uracil in DNA can occur due to deamination of cytosine, a spontaneous chemical reaction that converts cytosine to uracil.

This process is significant because uracil in DNA can lead to mutations. If DNA replication occurs when uracil is present, the replication machinery might mistakenly pair uracil with adenine, leading to a C-G to T-A transition mutation. Cells have evolved repair mechanisms, such as the uracil DNA glycosylase (UDG) enzyme, to detect and remove uracil from DNA. UDG excises the uracil base, creating an apurinic/apyrimidinic (AP) site, which is then repaired by other DNA repair enzymes.

The presence and removal of uracil are crucial for maintaining the integrity of the genome. While uracil is a fundamental component of RNA, its presence in DNA is generally considered an error that requires correction. In some cases, viruses also utilize uracil in their DNA, and understanding uracilation and its repair can be relevant to antiviral research. The study of uracilation contributes to our understanding of DNA repair pathways and their importance in preventing genetic instability and disease.