Dual cytosine modification through hydroxylation and arabinofuranosylation in phages.

Coliphage HY126 encodes a novel two-step arabinofuranosylation system that modifies cytosine with diarabinofuranosyl-5-hydroxycytosine in DNA.

• Why it matters: Understanding phage DNA modifications reveals strategies used in the phage-host evolutionary arms race, which can impact bacterial resistance and phage therapy development.
• What they did: The study identified a multienzyme cascade involving AfhB, AfhE, AfhF, AfhC, and AfhG, with AfhB hydroxylating dCMP to 5-hydroxy-dCMP and AfhC and AfhG adding arabinofuranose moieties to DNA.
• The result: This discovery uncovers a unique enzymatic mechanism for cytosine modification, expanding knowledge of phage DNA chemistry and potentially informing biotechnological applications.