Zinc-finger proteins contain DNA-binding domains and have a wide variety of functions, most of which encompass some form of transcriptional activation or repression. The majority of zinc-finger proteins contain a Krüppel-type DNA binding domain and a KRAB domain, which is thought to interact with KAP1, thereby recruiting histone modifying proteins. ZNF81, also known as HFZ20 or MRX45, is a transcriptional regulator belonging to the Krüppel C2H2-type zinc-finger protein family. It localizes to the nucleus and contains 12 C2H2-type zinc fingers and 1 KRAB domain. Mutations in the gene encoding ZNF81 are implicated in nonsyndromic X-linked mental retardation (XLMR).