Kruppel-like zinc finger proteins such as ZNF189 contain a conserved stretch of 7 amino acids that connects a variable number of DNA-binding zinc finger repeats of the cys(2)his(2) (C2H2) type. Approximately 30% of human Kruppel-like zinc finger proteins contain an N-terminal Kruppel-associated box (KRAB) domain. The KRAB domain consists of approximately 75 amino acids that may be subdivided into an A box, which is present in every KRAB domain and is essential for transcriptional repression, and a B box, which is not always present.