DUX4 (double homeobox 4)

Homeobox domains are a ~60 amino acid DNA binding motif conserved in many transcription factors involved in development (e.g. Hox genes). Double homeobox genes are a class of homeobox genes, specific to placental mammals, comprised of two closely spaced PRD-class homeobox domains. The Y-chromosome contains four DUX4-like genes, DUX4L16-19. While all four copies are present in both human and chimpanzee, three of the four copies in the chimpanzee genome have acquired premature stop codons leaving only DUX4L16 still able to encode a functional protein. As DUX4L16 is retained in both human and chimpanzee, and the human copies of DUX4L17-19 have undergone accelerated evololution, it has been proposed that DUX4L17-19 underwent neo-functionalization.