The human gene encodes a protein containing one KRAB domain and twelve zf-C2H2 domains. Domain order of chimpanzee homologous gene and gibbon orthologous gene resembles human gene, while rhesus homologous gene differs. We could not infer the ancestral state. Either loss of sequences in rhesus lineage or gain of sequences in the common ancestral lineage of human, chimpanzee and gibbon could be an explanation.