title: Evidence of neofunctionalization after the duplication of the highly conserved Polycomb group gene Caf1-55 in the obscura group of Drosophila.
abstract: Drosophila CAF1-55 protein is a subunit of the Polycomb repressive complex PRC2 and other protein complexes. It is a multifunctional and evolutionarily conserved protein that participates in nucleosome assembly and remodelling, as well as in the epigenetic regulation of a large set of target genes. Here, we describe and analyze the duplication of Caf1-55 in the obscura group of Drosophila. Paralogs exhibited a strong asymmetry in evolutionary rates, which suggests that they have evolved according to a neofunctionalization process. During this process, the ancestral copy has been kept under steady purifying selection to retain the ancestral function and the derived copy (Caf1-55dup) that originated via a DNA-mediated duplication event ~18 Mya, has been under clear episodic selection. Different maximum likelihood approaches confirmed the action of positive selection, in contrast to relaxed selection, on Caf1-55dup after the duplication. This adaptive process has also taken place more recently during the divergence of D. subobscura and D. guanche. The possible association of this duplication with a previously detected acceleration in the evolutionary rate of three CAF1-55 partners in PRC2 complexes is discussed. Finally, the timing and functional consequences of the Caf1-55 duplication is compared to other duplications of Polycomb genes.
authors.affiliation: Departament de Genètica, Microbiologia i Estadística, Facultat de Biologia, i Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Calvo-Martín
authors.affiliation: Departament de Genètica, Microbiologia i Estadística, Facultat de Biologia, i Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Papaceit
authors.affiliation: Departament de Genètica, Microbiologia i Estadística, Facultat de Biologia, i Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Segarra
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004330:Drosophila / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D019143:Evolution, Molecular; D020440:Gene Duplication; D017344:Genes, Insect; D010802:Phylogeny; D011110:Polymorphism, Genetic; D014157:Transcription Factors / Q000235:genetics*
chemical_list: C489780:CNOT8 protein, human; D014157:Transcription Factors