Sequence analysis of the mitochondrial genome of Sarcophyton glaucum: conserved gene order among octocorals

The nucleotide sequence for an 11,715-bp segment of the mitochondrial genome of the octocoral Sarcophyton glaucum is presented, completing the analysis of the entire genome for this anthozoan member of the phylum Cnidaria. The genome contained the same 13 protein-coding and 2 ribosomal RNA genes as in other animals. However, it also included an unusual mismatch repair gene homologue reported previously and codes for only a single tRNA gene. Intermediate in length compared to two other cnidarians (17,443 and 18,911 bp), this organellar genome contained the smallest amount of noncoding DNA (428, compared to 1283 and 781 nt, respectively), making it the most compact one found for the phylum to date. The mitochondrial genes of S. glaucum exhibited an identical arrangement to that found in another octocoral, Renilla kolikeri, with five protein-coding genes in the same order as has been found in insect and vertebrate mitochondrial genomes. Although gene order appears to be highly conserved among octocorals, compared to the hexacoral, Metridium senile, few similarities were found. Like other metazoan mitochondrial genomes, the A + T composition was elevated and a general bias against codons ending in G or C was observed. However, an exception to this was the infrequent use of TGA compared to TGG to code for tryptophan. This divergent codon bias is unusual but appears to be a conserved feature among two rather distantly related anthozoans.     

Gene rearrangements in snake mitochondrial genomes: highly concerted evolution of control-region-like sequences duplicated and inserted into a tRNA gene cluster

Mitochondrial DNA (mtDNA) regions corresponding to two major tRNA gene clusters were amplified and sequenced for the Japanese pit viper, himehabu. In one of these clusters, which in most vertebrates characterized to date contains three tightly connected genes for tRNA(Ile), and tRNA(Gln), and tRNA(Met), a sequence of approximately 1.3 kb was found to be inserted between the genes for tRNA(Ile) and tRNA(Gln). The insert consists of a control-region-like sequence possessing some conserved sequence blocks, and short flanking sequences which may be folded into tRNA(Pro), tRNA(Phe), and tRNA(Leu) genes. Several other snakes belonging to different families were also found to possess a control-region-like sequence and tRNA(Leu) gene between the tRNA(Ile)and tRNA(Gln) genes. We also sequenced a region surrounded by genes for cytochrome b and 12S rRNA, where the control region and genes for tRNA(Pro) and tRNA(Phe) are normally located in the mtDNAs of most vertebrates. In this region of three examined snakes, a control-region-like sequence exists that is almost completely identical to the one found between the tRNA(Ile) and tRNA(Gln) genes. The mtDNAs of these snakes thus possess two nearly identical control-region-like sequences which are otherwise divergent to a large extent between the species. These results suggest that the duplicate state of the control-region-like sequences has long persisted in snake mtDNAs, possibly since the original insertion of the control-region-like sequence and tRNA(Leu) gene into the tRNA gene cluster, which occurred in the early stage of the divergence of snakes. It is also suggested that the duplicated control-region-like sequences at two distant locations of mtDNA have evolved concertedly by a mechanism such as frequent gene conversion. The secondary structures of the determined tRNA genes point to the operation of simplification pressure on the T psi C arm of snake mitochondrial tRNAs.     

The fungal mitochondrial genome project: evolution of fungal mitochondrial genomes and their gene expression

The goal of the fungal mitochondrial genome project (FMGP) is to sequence complete mitochondrial genomes for a representative sample of the major fungal lineages; to analyze the genome structure, gene content, and conserved sequence elements of these sequences; and to study the evolution of gene expression in fungal mitochondria. By using our new sequence data for evolutionary studies, we were able to construct phylogenetic trees that provide further solid evidence that animals and fungi share a common ancestor to the exclusion of chlorophytes and protists. With a database comprising multiple mitochondrial gene sequences, the level of support for our mitochondrial phylogenies is unprecedented, in comparison to trees inferred with nuclear ribosomal RNA sequences. We also found several new molecular features in the mitochondrial genomes of lower fungi, including: (1) tRNA editing, which is the same type as that found in the mitochondria of the amoeboid protozoan Acanthamoeba castellanii; (2) two novel types of putative mobile DNA elements, one encoding a site-specific endonuclease that confers mobility on the element, and the other constituting a class of highly compact, structured elements; and (3) a large number of introns, which provide insights into intron origins and evolution. Here, we present an overview of these results, and discuss examples of the diversity of structures found in the fungal mitochondrial genome.     

The immunoglobulin superfamily: an insight on its tissular, species, and functional diversity

The immunoglobulin superfamily (IgSF) is a heterogenic group of proteins built on a common fold, called the Ig fold, which is a sandwich of two beta sheets. Although members of the IgSF share a similar Ig fold, they differ in their tissue distribution, amino acid composition, and biological role. In this paper we report an up-to-date compilation of the IgSF where all known members of the IgSF are classified on the basis of their common functional role (immune system, antibiotic proteins, enzymes, cytokine receptors, etc.) and their distribution in tissue (neural system, extracellular matrix, tumor marker, muscular proteins, etc.), or in species (vertebrates, invertebrates, bacteria, viruses, fungi, and plants). The members of the family can contain one or many Ig domains, comprising two basic types: the constant domain (C), with seven strands, and the variable domain (V), with eight, nine, or ten strands. The different overviews of the IgSF led to the definition of new domain subtypes, mainly concerning the C type, based on the distribution of strands within the two sheets. The wide occurrence of the Ig fold and the much less conserved sequences could have developed from a common ancestral gene and/or from a convergent evolutionary process. Cell adhesion and pattern recognition seem to be the common feature running through the entire family.     

The mitochondrial genome of the sea anemone Metridium senile (Cnidaria): introns, a paucity of tRNA genes, and a near-standard genetic code

The circular, 17,443 nucleotide-pair mitochondrial (mt) DNA molecule of the sea anemone, Metridium senile (class Anthozoa, phylum Cnidaria) is presented. This molecule contains genes for 13 energy pathway proteins and two ribosomal (r) RNAs but, relative to other metazoan mtDNAs, has two unique features: only two transfer RNAs (tRNA(f-Met) and tRNA(Trp)) are encoded, and the cytochrome c oxidase subunit I (COI) and NADH dehydrogenase subunit 5 (ND5) genes each include a group I intron. The COI intron encodes a putative homing endonuclease, and the ND5 intron contains the molecule's ND1 and ND3 genes. Most of the unusual characteristics of other metazoan mtDNAs are not found in M. senile mtDNA: unorthodox translation initiation codons and partial translation termination codons are absent, the use of TGA to specify tryptophan is the only genetic code modification, and both encoded tRNAs have primary and secondary structures closely resembling those of standard tRNAs. Also, with regard to size and secondary structure potential, the mt-s-rRNA and mt-1-rRNA have the least deviation from Escherichia coli 16S and 23S rRNAs of all known metazoan mt-rRNAs. These observations indicate that most of the genetic variations previously reported in metazoan mtDNAs developed after Cnidaria diverged from the common ancestral line of all other Metazoa.     

The flagellin gene of Borrelia miyamotoi sp. nov. and its phylogenetic relationship among Borrelia species

We have cloned and sequenced the flagellin gene from Borrelia miyamotoi strain HT31 and compared it with previously published flagellin sequences. Sequence similarity analysis demonstrated that strain HT31 is phylogenetically distant from the three species of Lyme disease borreliae is deeply branched into the relapsing fever borrelia cluster. The result was in full agreement with the classification of Borrelia strains using 16S tRNA sequences. This finding indicates that a phylogenetic analysis using flagellin gene sequences might be useful for classification of Borrelia strains.     

The evolution of primate malaria parasites based on the gene encoding cytochrome b from the linear mitochondrial genome

We report a phylogenetic analysis of primate malaria parasites based on the gene encoding the cytochrome b protein from the mitochondrial genome. We have studied 17 species of Plasmodium, including 14 parasitic in primates. In our analysis, four species were used for rooting the Plasmodium phylogenetic tree: two from closely related genera (Hepatocystis sp. and Haemoproteus columbae) and two other Apicomplexa (Toxoplasma gondii and Theileria parva). We found that primate malaria parasites form a monophyletic group, with the only exception being the Plasmodium falciparum-Plasmodium reichenowi lineage. Phylogenetic analyses that include two species of non-Plasmodium Haemosporina suggest that the genus Plasmodium is polyphyletic. We conclude that the biologic traits, such as periodicity and the capacity to relapse, have limited value for assessing the phylogenetic relationships among Plasmodium species. For instance, we found no evidence that would link virulence with the age of the host-parasite association. Our studies also reveal that the primate malaria parasites originated in Africa, which contradicts the presently held opinion of Southeast Asia as their center of origin. We propose that the radiation of Asian monkey parasites is a recent event where several life history traits, like differences in periodicity, appeared de novo.     

The mitochondrial genome integrity gene, MGI1, of Kluyveromyces lactis encodes the beta-subunit of F1-ATPase

In a previous report, we found that mutations at the mitochondrial genome integrity locus, MGI1, can convert Kluyveromyces lactis into a petite-positive yeast. In this report, we describe the isolation of the MGI1 gene and show that it encodes the beta-subunit of the mitochondrial F1-ATPase. The site of mutation in four independently isolated mgi1 alleles is at Arg435, which has changed to Gly in three cases and Ile in the fourth isolate. Disruption of MGI1 does not lead to the production of mitochondrial genome deletion mutants, indicating that an assembled F1 complex is needed for the "gain-of-function" phenotype found in mgi1 point mutants. The location of Arg435 in the beta-subunit, as deduced from the three-dimensional structure of the bovine F1-ATPase, together with mutational sites in the previously identified mgi2 and mgi5 alleles, suggests that interaction of the beta- and alpha- (MGI2) subunits with the gamma-subunit (MGI5) is likely to be affected by the mutations.     

Exhaustive scanning approach to screen all the mitochondrial tRNA genes for mutations and its application to the investigation of 35 independent patients with mitochondrial disorders

There have been several reports that thymoma in human is a progressive disease, and that thymoma and thymic carcinoma form a continuum. We established a stable line of SV40T transgenic mice, which consistently produced thymic epithelial tumours progressing to thymic carcinoma within a predictable time span. Using this animal model and a morphological approach, thymic epithelial tumour progression was studied with reference to sequential changes at different time points in animals aged from 3 to 32 weeks. At all ages, SV40T was expressed in the nuclei of thymic epithelial cells; in these transgenic mice we observed the entire spectrum from cortical type thymoma to thymic carcinoma. Thymic size tended to increase with ageing in SV40T TG mice. While younger mice had predominantly cortical (organoid) or cortical thymoma, older mice had well-differentiated thymic carcinoma (WDTC) or poorly differentiated thymic carcinoma. When SV40T TG mice (248 line) reached a certain age, carcinoma of the thymus was present in all of them. Cortical-type thymoma became malignant within a predictable time span, suggesting a cortical thymoma-carcinoma sequence. When the mice were 9 weeks of age, the thymuses formed gross masses compatible with cortical thymoma. At 14 weeks of age, WDTC appeared against the background of cortical thymoma. Poorly differentiated thymic carcinoma was found after 15 weeks and affected all animals over 23 weeks of age. Most thymic carcinomas coexisted in varying proportions with cortical-type thymoma. Medullary thymomas did not develop in the mice, and no transition from medullary-type thymomas to thymic carcinomas was observed. In this SV40T transgenic mouse model, thymic carcinoma is clearly preceded by cortical-type thymoma. These transgenic mice may provide an interesting model for the progression from cortical thymoma to WDTC and/or high-grade carcinoma.     

Genomic disorders: structural features of the genome can lead to DNA rearrangements and human disease traits

Molecular medicine began with Pauling's seminal work, which recognized sickle-cell anemia as a molecular disease, and with Ingram's demonstration of a specific chemical difference between the hemoglobins of normal and sickled human red blood cells. During the four decades that followed, investigations have focused on the gene--how mutations specifically alter DNA and how these changes affect the structure and expression of encoded proteins. Recently, however, the advances of the human genome project and the completion of total genome sequences for yeast and many bacterial species, have enabled investigators to view genetic information in the context of the entire genome. As a result, we recognize that the mechanisms for some genetic diseases are best understood at a genomic level. The evolution of the mammalian genome has resulted in the duplication of genes, gene segments and repeat gene clusters. This genome architecture provides substrates for homologous recombination between nonsyntenic regions of chromosomes. Such events can result in DNA rearrangements that cause disease.     

Exon-intron structure of the fet5+ gene of Schizosaccharomyces pombe and physical mapping of genome encompassing regions]

Groups of young male adult guinea pigs were fed a diet devoid in supplemental ascorbic acid (AA) or the same diet supplemented with 0.1 or 2.5% AA for four weeks. The animals were then euthanized and Phase I and Phase II drug metabolizing components in the liver were determined. Phase I components are those related to the metabolism of xenobiotics and include microsomal cytochrome P-450 and mixed function oxygenase activities. Phase II components are those related to conjugation and detoxification reactions of xenobiotics and their metabolites and include glutathione-S-transferases (GST), glutathione (GSH), UDP-glucuronyl transferase (UDP-GT) and DT-diaphorase (quinone reductase, QR). Tissue levels of AA increased progressively with increase in AA intake. The Phase I components increased in response to increased intake of AA from 0 to 0.1%, but were unaffected by further increase in AA intake to 2.5%. However, the Phase II components increased with increased intake of AA except for GST. In vitro metabolism of aflatoxin B1 (AFB1) using liver microsomes showed tendency towards increased production of aflatoxin M1 (AFM1) with increase in AA intake. The production of aflatoxin P1 (AFP1) was not affected by AA intake. AFB1-DNA production was increased when AA intake was increased to 0.1%. It was however lowered with further increase in AA intake to 2.5%.     

Effect of the amino acid attached to Escherichia coli initiator tRNA on its affinity for the initiation factor IF2 and on the IF2 dependence of its binding to the ribosome

We show that the nature of the amino acid in the formylaminoacyl-tRNA influences initiation factor (IF) 2 dependence of its ribosome binding and that this IF2 dependence reflects the relative affinity of the formylaminoacyl-tRNA for the initiation factor IF2. We compared the template-dependent ribosome binding activities, in the presence of initiation factors, of wild type and anticodon sequence mutants of Escherichia coli initiator tRNAs that carry formylmethionine (fMet), formylglutamine (fGln), or formylvaline (fVal). The fGln-tRNA bound less well than fMet-tRNA whereas the fVal-tRNA bound as well as fMet-tRNA. The rate and extent of binding of fGln-tRNA to the ribosome was significantly increased by further addition of purified initiation factor IF2. In contrast, the binding of fVal-tRNA or fMet-tRNA was not affected much by the addition of IF2. Using gel mobility shift assay, we have measured the apparent Kd values of the IF2.formylaminoacyl-tRNA binary complexes. These are 1.8, 3.5, and 10.5 microM for fMet-tRNA, fVal-tRNA, and fGln-tRNA, respectively.     

Distribution of the trehalase activation response and the regulatory trehalase gene among yeast species

In Saccharomyces cerevisiae and other yeasts the activity of regulatory trehalases increases in response to the addition of glucose and to thermal changes in the extracellular medium. We have performed an screening on the extent of this response among different representative yeast species and the results show that this ability is displayed only by a few members of the Saccharomycetaceae family. However, all yeasts examined contain a gene related to that coding for regulatory trehalase in S. cerevisiae. This finding reveals that the operational distinction between regulatory and nonregulatory trehalase in yeasts is not a property of the enzyme by itself but relays on the expression of accompanying mechanisms able to modulate trehalase activity.     

The frequency of a common mutation of the methionine synthase gene in the Australian population and its relation to smoking and coronary artery disease

BACKGROUND: Modest elevations in levels of circulating homocysteine are common in patients with vascular disease. Methionine synthase is a vitamin B12-dependent enzyme catalysing the re-methylation of homocysteine to methionine; reduced methionine synthase activity results in elevated level of homocysteine. DESIGN: A case-control study. METHODS: We explored the frequency and distribution of a 2756A-->G (D919G) mutation of the methionine synthase gene, detected by polymerase chain reaction genotyping, in 745 Australian Caucasian patients aged < or = 65 years (550 men and 195 women) with and without angiographically documented coronary artery disease (CAD). RESULTS: The frequency distributions of AA, AG and GG genotypes were 61.9%, 33.8% and 4.3%, respectively, and were in Hardy-Weinberg equilibrium. There was no correlation between the methionine synthase mutation and CAD from simple chi2 comparison. However, the interactive term of life-time smoking dose with methionine synthase genotypes was predictive of both the number of significantly diseased vessels (> or =50% luminal obstruction; chi2 = 12.518, P=0.0019), and the presence or absence of significant CAD (chi2=7.045, P=0.027). A stepwise logistic regression analysis showed that smokers who were also GG homozygotes had more severe CAD compared with smokers of other genotypes. The methionine synthase genotypes were not associated with any of the other established CAD risk factors assessed in our study. CONCLUSIONS: We conclude that the methionine synthase 2756A-->G mutation is common, with homozygosity occurring in approximately 4% of white Australians, and that it has an interactive effect with life-time smoking dose to increase the severity of CAD. Smokers who are also GG homozygotes have additionally elevated CAD risk.     

The development of an idiographic measure of self-schemas: An illustration of the construction and use of self-scenarios.

Self-scenarios were used as a repeated measures outcome measurement with a 41-yr-old unemployed White male patient with a history of anxiety and depression. Self-scenarios represent an idiographic measure of dysfunctional schemas, defined as cognitive-affective-motoric structures. Two psychologists acted as assessment interviewer and 3rd-party observer. After the 2nd session, S rated 5 self-scenarios (appended) corresponding to his own problems for frequency, preoccupation, accessibility, alternatives, self-efficacy, self-view, interpersonal view, and chronicity. From the 3rd to 20th session, S received only the 2 clinically relevant scenarios and completed corresponding ratings. General psychiatric symptomatology was measured at treatment outcome. Not all indices displayed the same magnitude of change or the same time frame for change; change was not maintained in a linear fashion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic rearrangements leading to disruption of heterologous gene expression in mycobacteria: an observation with Escherichia coli beta-galactosidase in Mycobacterium smegmatis and its implication in vaccine development

Different mycobacteria carrying cloned genes for heterologous protective antigens have been proposed as vaccine vehicles. In this study, the stability of the expression of beta-galactosidase was studied in Mycobacterium smegmatis using integrative (pMV361::lacZ) and replicative (pMV261::lacZ) vectors. Recombinant M. smegmatis forms blue colonies on X-gal plates. Occasional white mutants encountered while plating on X-gal plates were genetically analysed. The loss of lacZ phenotype was due to insertion of an IS element in lacZ gene of integrative vector whereas in case of replicative vectors, loss of lacZ phenotype was due to deletions of different sizes in the lacZ gene and the Phsp60 promoter region. The frequency of such events was rare, 1.7 x 10(-5) in integrative vector and 2 x 10(-3) in the case of replicative vector. The integrative vector seemed more stable in terms of expression of foreign genes in mycobacteria. Hence, the rearrangements reported in the present study warrant serious consideration before implementing mycobacteria as recombinant vaccines.