Crosslink and shield: protecting abasic sites from error-prone repair

Abasic sites are among the most frequent DNA lesions, and when they occur within single-stranded DNA, their repair can give rise to genomic instability and mutations. One mechanism for the protection of abasic sites involves covalent attachment of 5-hydroxymethylcytosine-binding, embryonic stem cell–specific (HMCES) protein to DNA. Now, two research groups have elucidated the structural basis of the action of HMCES and its bacterial equivalent, YedK, revealing a unique and intriguing chemistry of DNA–protein crosslink formation. © 2019, Springer Nature America, Inc.