Laboratoire de Biologie Moléculaire et de Génie Génétique, Université de Liège, Sart Tilman, Belgium.
We have previously shown that the human genome includes hundreds of genes coding for putative factors related to the Krüppel zinc-finger protein, which regulates Drosophila segmentation. We report herein that about one-third of these genes code for proteins that share a very conserved region of about 75 amino acids in their N-terminal nonfinger portion. Homologous regions are found in a number of previously described finger proteins, including mouse Zfp-1 and Xenopus Xfin. We named this region the Krüppel-associated box (KRAB). This domain has the potential to form two amphipathic alpha-helices. Southern blot analysis of "zoo" blots suggests that the Krüppel-associated box is highly conserved during evolution. Northern blot analysis shows that these genes are expressed in most adult tissues and are down-regulated during in vitro terminal differentiation of human myeloid cells.