Mer22-related sequence elements form pericentric repetitive DNA families in primates

We describe a novel repetitive DNA element isolated from three primate species belonging to the family Cercopithecidae. The unusually long 2.6-kb repeat unit of this DNA element is present in high copy number in the pericentromeric region of one pair of chromosomes in both baboon and macaque, forming chromosome-specific satellite-like DNA families. Besides these two very closely related species, the novel DNA element was also detected in the more distantly related African green monkey. However, the copy number of the repeat unit in this species is significantly lower than in macaque and baboon. Sequence analysis revealed that the repeat units of the new repetitive element show similarity to the human MER22 repeat and the Y chromosome-specific TTY2 element, which also exhibits retroelement-like features. Database searches indicate that tandemly arranged MER22-related DNA sequences can also be found in human, raising the possibility that these DNA elements may correspond to a novel primate-specific repetitive DNA group. Recent studies indicate that chromosome-specific pericentric repetitive elements, besides their potential involvement in centromere function, also facilitate homolog recognition during meiosis. In addition, rapid expansion of retroelements in the pericentric regions of chromosomes during interspecific hybridization has been described. In light of these data, we hypothesize that the novel repetitive element described here might have been involved in the speciation of the family Cercopithecidae.