Fig. 1.

KRAB-ZnF proteins. The SysZNF database was examined for Krüppel-associated box (KRAB)-ZnF proteins in human (A) or mouse (B). In each case, the distribution of KRAB-ZnF proteins containing a given number of ZnF repeats is shown. (C) Examples of mammalian KRAB-ZnF proteins with known biologic roles. The size of each protein (in amino acids) is shown on the right. The classic C2H2 ZnF motifs are shown in blue (gray in the print version) boxes and the gray or open boxes indicate degenerate ZnFs that contain mutations affecting zinc coordination. The red (gray in the print version) boxes of mouse Zfp57 and human PRDM9 indicate the structurally characterized ZnFs in complex with their recognition sequences shown below. The amino acids within the red (gray in the print version) box indicate the three or four residues of each ZnF involved in base specific interactions. The SCAN box, a leucine-rich region, was named after SRE-ZBP, CTfin51, AW-1 (ZNF174), Number 18 cDNA (ZnF20) (Williams, Khachigian, Shows, & Collins, 1995). The SET domain was named after Su(var)3–9, Enhancer of zeste, Trithorax (Jenuwein, Laible, Dorn, & Reuter, 1998). Modified from Liu, Y., Zhang, X., Blumenthal, R. M., & Cheng, X. (2013). A common mode of recognition for methylated CpG. Trends in Biochemical Sciences, 38, 177–183.