title: Ancient Origin of Chaperonin Gene Paralogs Involved in Ciliopathies.
abstract: The Bardet-Biedl Syndrome (BBS) is a human developmental disorder that has been associated with fourteenBBSgenes affecting the development of cilia. ThreeBBSgenes are distant relatives of chaperonin proteins, a family of chaperones well known for the protein-folding role of their double-ringed complexes. Chaperonin-likeBBSgenes were originally thought to be vertebrate-specific, but related genes from different metazoan species have been identified as chaperonin-likeBBSgenes based on sequence similarity. Our phylogenetic analyses confirmed the classification of these genes in the chaperonin-likeBBSgene family, and set the origin of the gene family earlier than the time of separation of Bilateria, Cnidaria, and Placozoa. By extensive searches of chaperonin-like genes in complete genomes representing several eukaryotic lineages, we discovered the presence of chaperonin-likeBBSgenes also in the genomes ofPhytophthoraandPythium, belonging to the group of Oomycetes. This finding suggests that the chaperonin-like BBS gene family had already evolved before the origin of Metazoa, as early in eukaryote evolution as before separation of the lineages of Unikonts and Chromalveolates. The analysis of coding sequences indicated that chaperonin-like BBS proteins have evolved in all lineages under constraining selection. Furthermore, analysis of the predicted structural features suggested that, despite their high rate of divergence, chaperonin-like BBS proteins mostly conserve a typical chaperonin-like three-dimensional structure, but question their ability to assemble and function as chaperonin-like double-ringed complexes.
authors.affiliation: Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32610-3610, USA.
authors.forename: Krishanu
authors.initials: K
authors.lastname: Mukherjee
authors.forename: Luciano
authors.initials: L
authors.lastname: Brocchieri