Analyses of an Expressed Sequence Tag Library from Taenia solium, Cysticerca

A method used to describe expressed genes at a specific stage in an organism is an EST library. In this method mRNA from a specific organism is isolated, transcribed into cDNA and sequenced. The sequence will derive from the 5′-end of the cDNA. The library will not have sequences from all genes, especially if they are expressed in low amounts or not at all in the studied stage. Also the library will mostly not contain full length sequences from genes, but expression patterns can be established. If EST libraries are made from different stages of the same organisms these libraries can be compared and differently expressed genes can be identified. Described here is an analysis of an EST library from the pig cysticerca which is thought to be similar to the stage giving the human neglected disease neurocysticercosis. Novel genes together with putative drug targets are examples of data presented

Targeting of mutant hogg1 in mammalian mitochondria and nucleus: effect on cellular survival upon oxidative stress

BACKGROUND: Oxidative damage to mitochondrial DNA has been implicated as a causative factor in a wide variety of degenerative diseases, aging and cancer. The modified guanine, 7,8-dihydro-8-oxoguanine (also known as 8-hydroxyguanine) is one of the major oxidized bases generated in DNA by reactive oxygen species and has gained most of the attention in recent years as a marker of oxidative DNA injury and its suspected role in the initiation of carcinogenesis. 8-hydroxyguanine is removed by hOgg1, a DNA glycosylase/AP lyase involved in the base excision repair pathway. METHODS: We over-expressed wild type and R229Q mutant hOGG1 in the nucleus and mitochondria of cells lacking mitochondrial hOGG1 expression through an expression vector containing nuclear and mitochondrial targeting sequence respectively. We used quantitative real time PCR to analyze mtDNA integrity after exposure to oxidative damaging agents, in cells transfected with or without mitochondrially-targeted mutant hogg1. RESULT: Over-expression of wild type hOgg1 in both nucleus and mitochondria resulted in increased cellular survival when compared to vector or mutant over-expression of hOGG1. Interestingly, mitochondrially-targeted mutant hogg1 resulted in more cell death than nuclear targeted mutant hogg1 upon exposure of cells to oxidative damage. Additional we examined mitochondrial DNA integrity after oxidative damage exposure using real-time quantitative PCR. The presence of mutant hogg1 in the mitochondria resulted in reduced mitochondrial DNA integrity when compared to the wild type. Our work indicates that the R229Q hOGG1 mutation failed to protect cells from oxidative damage and that such mutations in cancer may be more detrimental to cellular survival when present in the mitochondria than in the nucleus. CONCLUSION: These findings suggest that deficiencies in hOGG1, especially in the mitochondria may lead to reduced mitochondrial DNA integrity, consequently resulting in decreased cell viability

The Minimal Proteome in the Reduced Mitochondrion of the Parasitic Protist Giardia intestinalis

The mitosomes of Giardia intestinalis are thought to be mitochondria highly-reduced in response to the oxygen-poor niche. We performed a quantitative proteomic assessment of Giardia mitosomes to increase understanding of the function and evolutionary origin of these enigmatic organelles. Mitosome-enriched fractions were obtained from cell homogenate using Optiprep gradient centrifugation. To distinguish mitosomal proteins from contamination, we used a quantitative shot-gun strategy based on isobaric tagging of peptides with iTRAQ and tandem mass spectrometry. Altogether, 638 proteins were identified in mitosome-enriched fractions. Of these, 139 proteins had iTRAQ ratio similar to that of the six known mitosomal markers. Proteins were selected for expression in Giardia to verify their cellular localizations and the mitosomal localization of 20 proteins was confirmed. These proteins include nine components of the FeS cluster assembly machinery, a novel diflavo-protein with NADPH reductase activity, a novel VAMP-associated protein, and a key component of the outer membrane protein translocase. None of the novel mitosomal proteins was predicted by previous genome analyses. The small proteome of the Giardia mitosome reflects the reduction in mitochondrial metabolism, which is limited to the FeS cluster assembly pathway, and a simplicity in the protein import pathway required for organelle biogenesis

Structure of human mitochondrial RNA polymerase

Transcription of the mitochondrial genome is performed by a single-subunit RNA polymerase (mtRNAP) that is distantly related to the RNAP of bacteriophage T7, the pol I family of DNA polymerases, and single-subunit RNAPs from chloroplasts1, 2, 3, 4. Whereas T7 RNAP can initiate transcription by itself, mtRNAP requires the factors TFAM and TFB2M for binding and melting promoter DNA5, 6, 7. TFAM is an abundant protein that binds and bends promoter DNA 15–40 base pairs upstream of the transcription start site, and stimulates the recruitment of mtRNAP and TFB2M to the promoter8, 9. TFB2M assists mtRNAP in promoter melting and reaches the active site of mtRNAP to interact with the first base pair of the RNA–DNA hybrid10. Here we report the X-ray structure of human mtRNAP at 2.5 Å resolution, which reveals a T7-like catalytic carboxy-terminal domain, an amino-terminal domain that remotely resembles the T7 promoter-binding domain, a novel pentatricopeptide repeat domain, and a flexible N-terminal extension. The pentatricopeptide repeat domain sequesters an AT-rich recognition loop, which binds promoter DNA in T7 RNAP, probably explaining the need for TFAM during promoter binding. Consistent with this, substitution of a conserved arginine residue in the AT-rich recognition loop, or release of this loop by deletion of the N-terminal part of mtRNAP, had no effect on transcription. The fingers domain and the intercalating hairpin, which melts DNA in phage RNAPs, are repositioned, explaining the need for TFB2M during promoter melting. Our results provide a new venue for the mechanistic analysis of mitochondrial transcription. They also indicate how an early phage-like mtRNAP lost functions in promoter binding and melting, which were provided by initiation factors in trans during evolution, to enable mitochondrial gene regulation and the adaptation of mitochondrial function to changes in the environment

Vaccination against helminth parasite infections

Helminth parasites infect over one fourth of the human population and are highly prevalent in livestock worldwide. In model systems, parasites are strongly immunomodulatory, but the immune system can be driven to expel them by prior vaccination. However, no vaccines are currently available for human use. Recent advances in vaccination with recombinant helminth antigens have been successful against cestode infections of livestock and new vaccines are being tested against nematode parasites of animals. Numerous vaccine antigens are being defined for a wide range of helminth parasite species, but greater understanding is needed to define the mechanisms of vaccine-induced immunity, to lay a rational platform for new vaccines and their optimal design. With human trials underway for hookworm and schistosomiasis vaccines, a greater integration between veterinary and human studies will highlight the common molecular and mechanistic pathways, and accelerate progress towards reducing the global health burden of helminth infection