A recombination hotspot in a schizophrenia-associated region of GABRB2.

Background: Schizophrenia is a major disorder with complex genetic mechanisms. Earlier, population genetic studies revealed the occurrence of strong positive selection in the GABRB2 gene encoding the beta(2) subunit of GABA(A) receptors, within a segment of 3,551 bp harboring twenty-nine single nucleotide polymorphisms (SNPs) and containing schizophrenia-associated SNPs and haplotypes.

Methodology/principal Findings: In the present study, the possible occurrence of recombination in this 'S1-S29' segment was assessed.

Positive selection within the Schizophrenia-associated GABA(A) receptor beta(2) gene.

The gamma-aminobutyric acid type-A (GABA(A)) receptor plays a major role in inhibitory neurotransmissions. Intronic SNPs and haplotypes in GABRB2, the gene for GABA(A) receptor beta(2) subunit, are associated with schizophrenia and correlated with the expression of two alternatively spliced beta(2) isoforms. In the present study, using chimpanzee as an ancestral reference, high frequencies were observed for the derived (D) alleles of the four SNPs rs6556547, rs187269, rs1816071 and rs1816072 in GABRB2, suggesting the occurrence of positive selection for these derived alleles.

GABRB2 association with schizophrenia: commonalities and differences between ethnic groups and clinical subtypes.

Background: Single nucleotide polymorphisms (SNPs) and haplotypes in intron 8 of type A gamma-aminobutyric acid (GABA(A)) receptor beta2 subunit gene (GABRB2) were initially found to be associated with schizophrenia in Chinese. This finding was subjected to cross-validation in this study with Japanese (JP) and German Caucasian (GE) subjects.

Methods: Single nucleotide polymorphisms discovery and genotyping were carried out through resequencing of a 1839 base pair (bp) region in GABRB2.

Congruence of evidence for a Methanopyrus-proximal root of life based on transfer RNA and aminoacyl-tRNA synthetase genes.

Among 60 organisms, the intraspecies genetic distances between tRNAs cognate for different amino acids, between the initiator and elongator tRNAs for Met, and between potentially paralogous pairs of aminoacyl-tRNA synthetases are found to be at a minimum within the Methanopyrus kandleri genome. These results indicate an exact congruence between the evidence from tRNA and aminoacyl-tRNA synthetase genes locating the root of life closest to this organism.

Anticodon and wobble evolution.

The location of the root of life within the Archaea domain close to Methanopyrus kandleri and Aeropyrum pernix on the basis of tRNA sequence clustering has allowed the tracing of evolutionary change in anticodon usages and the wobble rules governing them among different living lineages. Analysis suggests that the primitive Archaea employed simple modes of wobble of anticodon-codon pairing that enable the reading of standard one-amino acid and two-amino acid odon boxes with the uniform use of GNN and UNN anticodons, or the uniform use of GNN, UNN and CNN anticodons, together with the use of a modified C to read the AUA codon of isoleucine. Later on, evolution of tRNA sequences and posttranscriptional modifications brought about in the Bacteria and Eukarya the more complex anticodon usages as described by the Crick Rules of wobble, often with different codon boxes being read with dissimilar anticodon combinations.

Transfer RNA paralogs: evidence for genetic code-amino acid biosynthesis coevolution and an archaeal root of life.

A search has been performed on 2878 tRNA sequences from 60 different genomes in order to detect the existence of closely related 'alloacceptor' tRNAs accepting dissimilar amino acids that could be paralogs generated by gene duplications. This has led to the identification of extremely conserved tRNA(Phe)-tRNA(Tyr) pairs displaying as high as 94% identity between them, and also other potentially paralogous tRNA pairs in archaeal species. These paralogous pairs are enriched for amino acid pairs belonging to the same amino acid biosynthetic family, thus providing evidence for the coevolution of genetic code and amino acid biosynthesis.

NMR analysis of bovine tRNATrp: conformation dependence of Mg2+ binding.

NMR was used to study the solution structure of bovine tRNA(Trp) hyperexpressed in Escherichia coli. With the use of (15)N labeling and site-directed mutagenesis to assign overlapping resonances through the base pair replacement of U(71)A(2) by G(2)C(71), U(27)A(43) by G(27)C(43), and G(12)C(23) by U(12)A(23), the resonances of all 26 observable imino protons in the helical regions and in the tertiary interactions were assigned unambiguously by means of two-dimensional nuclear Overhauser effect spectroscopy and heteronuclear single quantum coherence methods. When the discriminator base A(73) and the G(12)C(23) base pair on the D stem, two identity elements on bovine tRNA(Trp) that are important for effective recognition by tryptophanyl-tRNA synthetase, were mutated to the ineffective forms of G(73) and U(12)A(23), respectively, NMR analysis revealed an important conformational change in the U(12)A(23) mutant but not in the G(73) mutant molecule.

Recognition by tryptophanyl-tRNA synthetases of discriminator base on tRNATrp from three biological domains.

To study the recognition by tryptophanyl-tRNA synthetase (TrpRS) of tRNA(Trp) discriminator base, mutations were introduced into the discriminator base of Bacillus subtilis, Archeoglobus fulgidus, and bovine tRNA(Trp), representing the three biological domains. When B. subtilis, A.