title: Dimorphisms of the proteasome subunit beta type 8 gene (PSMB8) of ectothermic tetrapods originated in multiple independent evolutionary events.
abstract: The proteasome subunit beta type 8 gene (PSMB8) encodes one of the beta subunits of the immunoproteasome responsible for the generation of peptides presented by major histocompatibility complex class I molecules. Dimorphic alleles of the PSMB8 gene, termed A and F types, based on the deduced 31st amino acid residue of the mature protein have been reported from various vertebrates. Phylogenetic analysis revealed the presence of dichotomous ancient lineages, one comprising the F-type PSMB8 of basal ray-finned fishes, and the other comprising the A-type PSMB8 of these animals and both the F- and A-type PSMB8 of Xenopus and acanthopterygians, indicating that evolutionary history of the PSMB8 dimorphism was not straightforward. We analyzed the PSMB8 gene of five reptile and one amphibian species and found both the A and F types from all six. Phylogenetic analysis indicated that the PSMB8 F type was apparently regenerated from the PSMB8 A type at least five times independently during tetrapod evolution. Genomic typing of wild individuals of geckos and newts indicated that the frequencies of the A- and F-type alleles are not highly biased in these species. Phylogenetic analysis of each exon of the reptile PSMB8 gene suggested interallelic sequence homogenization as a possible evolutionary mechanism for the apparent recurrent regeneration of PSMB8 dimorphism in tetrapods. An extremely strong balancing selection acting on PSMB8 dimorphism was implicated in an unprecedented pattern of allele evolution.
authors: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
authors: Ching-Huei
authors: CH
authors: Huang
authors: Yuta
authors: Y
authors: Tanaka
authors: Naoko T
authors: NT
authors: Fujito
authors: Masaru
authors: M
authors: Nonaka
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D005787:Gene Frequency; D008969:Molecular Sequence Data; D010802:Phylogeny; D011110:Polymorphism, Genetic / Q000235:genetics*; D046988:Proteasome Endopeptidase Complex / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013696:Temperature; D014714:Vertebrates / Q000235:genetics*
chemical_list: C077436:LMP7 protein; D046988:Proteasome Endopeptidase Complex
references: Structure. 2002 May;10(5):609-18
references: 12015144
references: Mol Biol Evol. 2011 Dec;28(12):3237-52
references: 21680872
references: Mol Biol Evol. 2012 Oct;29(10):3071-9
references: 22491037
references: Science. 1994 Aug 26;265(5176):1234-7
references: 8066463
references: Eur J Immunol. 2003 Nov;33(11):3017-27
references: 14579270
references: Nature. 2004 Dec 9;432(7018):695-716
references: 15592404
references: Mol Biol Evol. 1987 Jul;4(4):406-25
references: 3447015
references: J Immunol. 2002 Jan 15;168(2):771-81
references: 11777971
references: J Clin Invest. 2011 Oct;121(10):4150-60
references: 21881205
references: Hereditas. 1997;127(1-2):59-65
references: 9420471
references: Nature. 1997 Apr 3;386(6624):463-71
references: 9087403
references: Nucleic Acids Res. 2004 Mar 19;32(5):1792-7
references: 15034147
references: Immunol Rev. 1998 Jun;163:161-76
references: 9700509
references: J Mol Evol. 1980 Dec;16(2):111-20
references: 7463489
references: PLoS Biol. 2010 Sep 07;8(9):
references: 20838655
references: Proc Natl Acad Sci U S A. 2011 Sep 6;108(36):14914-9
references: 21852578
references: Nature. 2010 Apr 1;464(7289):757-62
references: 20360741
references: Immunogenetics. 2005 Jul;57(6):420-31
references: 16003465
references: Immunogenetics. 2012 Jun;64(6):447-53
references: 22322674
references: Proc Natl Acad Sci U S A. 2010 Dec 14;107(50):21599-604
references: 21098669
references: Mol Biol Evol. 2011 Oct;28(10):2731-9
references: 21546353
references: Science. 1994 Aug 26;265(5176):1231-4
references: 8066462
references: EMBO J. 1994 Jul 15;13(14):3236-44
references: 8045254
references: Am J Hum Genet. 2010 Dec 10;87(6):866-72
references: 21129723
references: Evolution. 1985 Jul;39(4):783-791
references: 28561359
references: Immunogenetics. 2000 Mar;51(3):186-92
references: 10752627