Concerted evolution of the keratin-associated protein-1 (KAP1) genes

Abstract

Keratin-associated proteins (KAPs) are a structural component of hair and wool fibers, and form the matrix between the keratin intermediate filaments. Up to 27 KAP families have been reported, of which KAP1 is probably the best characterized and diverse family. While the KAP1 genes have been characterized in several species, the orthologs in many other species remain un-identified and the evolution of these genes is poorly understood. In this study, the KAP1 genes from cattle, horses, rabbits and elephants were identified in the respective genome sequences. Sequence analyses revealed that the coding regions of the specific KAP1 family members in each species were much more closely related to each other, than to the same family members in other species. In contrast, the 5′ and 3′ regions flanking the genes were clustered across species into specific family members. Unique strings of amino acid residues were shared between family members from within a given species, or at times between closely related species. Shared nucleotide polymorphisms were also found across family members in the coding region in sheep. This suggests that the coding region of the KAP1 genes has been subjected to concerted evolution and that gene conversion-like events may be the driving force that leads to homogenization of the KAP1 coding sequences.