title: The evolution and genomic landscape of CGB1 and CGB2 genes.
abstract: The origin of completely novel proteins is a significant question in evolution. The luteinizing hormone (LHB)/chorionic gonadotropin (CGB) gene cluster in humans contains a candidate example of this process. Two genes in this cluster (CGB1 and CGB2) exhibit nucleotide sequence similarity with the other LHB/CGB genes, but as a result of frameshifting are predicted to encode a completely novel protein. Our analysis of these genes from humans and related primates indicates a recent origin in the lineage specific to humans and African great apes. While the function of these genes is not yet known, they are strongly conserved between human and chimpanzee and exhibit three-fold lower diversity than LHB across human populations with no mutations that would disrupt the coding sequence. The 5'-upstream region of CGB1/2 contains most of the promoter sequence of hCGbeta plus a novel region proximal to the putative transcription start site. In silico prediction of putative transcription factor binding sites supports the hypothesis that CGB1 and CGB2 gene products are expressed in, and may contribute to, implantation and placental development.
authors.affiliation: Department of Biotechnology, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia.
authors.forename: Pille
authors.initials: P
authors.lastname: Hallast
authors.forename: Kristiina
authors.initials: K
authors.lastname: Rull
authors.forename: Maris
authors.initials: M
authors.lastname: Laan
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000235:genetics*; D018389:Codon, Nonsense / Q000235:genetics; D017124:Conserved Sequence; D010064:Embryo Implantation / Q000235:genetics; D019143:Evolution, Molecular; D005091:Exons / Q000235:genetics; D016678:Genome / Q000235:genetics*; D023281:Genomics; D015186:Hominidae / Q000235:genetics*; D006801:Humans; D007438:Introns / Q000235:genetics; D007986:Luteinizing Hormone / Q000235:genetics; D008969:Molecular Sequence Data; D010920:Placenta / Q000196:embryology; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D018997:Chorionic Gonadotropin, beta Subunit, Human; D018389:Codon, Nonsense; D014157:Transcription Factors; D007986:Luteinizing Hormone