title: Lineage-specific homogenization of the polyubiquitin gene among human and great apes.
abstract: Ubiquitin is a highly conserved protein, and is encoded by a multigene family among eukaryote species. The polyubiquitin genes, UbB and UbC, comprise tandem multiple ubiquitin coding units without a spacer region or intron. We determined nucleotide sequences for the UbB and UbC of human, chimpanzee, gorilla, and orangutan. The ubiquitin repeat number of UbB was constant (3) in human and great apes, while that of UbC varied: 6 to 11 for human, 10 to 12 for chimpanzee, 8 for gorilla, and 10 for orangutan. The heterogeneity of the repeat number within closely related hominoid species suggests that a lineage-specific unequal crossover and/or gene duplication occurred. A marked homogenization of UbC occurred in gorilla with a low level of synonymous difference (p(s)). The homogenization of UbC also occurred in chimpanzee and less strikingly in human. The first and last ubiquitin coding units of UbC were clustered independently between species, and less affected by homogenization during the hominoid evolution. Therefore, the homogenization of ubiquitin coding units is likely due to an unequal crossing-over inside the ubiquitin units. The lineage-specific homogenization of UbC among closely related species suggests that concerted evolution has a key role in the short-term evolution of UbC.
authors.affiliation: Division of Genetic Diagnosis, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tachikui
authors.forename: Naruya
authors.initials: N
authors.lastname: Saitou
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Nakajima
authors.forename: Ikuo
authors.initials: I
authors.lastname: Hayasaka
authors.forename: Takafumi
authors.initials: T
authors.lastname: Ishida
authors.forename: Ituro
authors.initials: I
authors.lastname: Inoue
mesh_terms: D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D015186:Hominidae / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D025821:Polyubiquitin / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D025801:Ubiquitin / Q000235:genetics
chemical_list: D025801:Ubiquitin; D025821:Polyubiquitin; D004247:DNA