Fig. 2.—

Evolutionary tree showing relationships between KRAB domain sequences from human, opossum, chicken, and frog. (A) A circular tree showing clustering of sequences including all ZNF-associated KRAB domains from human (red), opossum (purple), chicken (blue), and frog (green) KRAB-ZNF gene models (see Materials and Methods). The boxed region is expanded and shown as a rectangular tree in (B). The KRAB domain of the Strongylocentrotus purpuratus PRDM9 protein was included to root the tree. The human ZNF282-related cluster dominates this branch of the tree which also includes isoforms of ZNF862, a KRAB-containing TTF-finger ZNF gene that also maps to the cluster region in human chromosome 7q36.1.