Analysis of compensatory substitution and gene evolution on the MAGEA/CSAG-palindrome of the primate X chromosomes

The human X chromosome contains a large number of inverted repeat DNA palindromes. Although arbitrary substitutions destroyed the inverted repeat structure of MAGEA/CSAG-palindrome during the evolutionary process of the primates, most of the substitutions are compensatory. Using maximum parsimony, it is demonstrated that the compensatory substitutions are prone to occur between bases with similar structures on the human, chimpanzee and orangutan MAGEA/CSAG-palindromes. Furthermore, it is found that MAGEA/CSAG genes also exist in orangutan and rhesus monkey palindromes by homologous searching. This suggests that the MAGEA/CSAG-palindrome might predate the divergence of human and other primate lineages. Comparative sequence analysis of the arms and genes on the primate MAGEA/CSAG-palindromes provides possible evidence of subsequently arm to arm gene conversion. These compensatory substitutions on the MAGEA/CSAG-palindrome of the primate X chromosomes play an important role in maintaining their structural symmetry during the process of formation.

Most of the substitutions on the MAGE/CSAG-palindromes are compensatory and are prone to occur within similar structures. Compensatory substitutions and further phylogenetic analysis of MAGEA/CSAG genes provides possible evidence of subsequently arm to arm gene conversion.Figure optionsDownload as PowerPoint slideHighlights
► Most of the substitutions on the MAGE/CSAG-palindromes are compensatory and are prone to occur within similar structures.
► The homologous genes exist in orangutan and rhesus monkey, which suggests that the palindrome might predate the divergence of human and other primate lineages.
► Compensatory substitutions and further phylogenetic analysis of MAGEA/CSAG genes provide possible evidence of subsequently arm to arm gene conversion.