Effect of dietary taurine supplementation on metabolome variation in plasma of Nile tilapia.

Taurine has been considered as an essential nutrient for many aquaculture species. While dietary taurine supplementation is highly recommended, novelty studies on taurine metabolism in fish are needed. The present study aimed to provide insight into the molecular mechanisms involved in multiple metabolome changes in Nile tilapia (Oreochromis niloticus) by studying plasma metabolic profile changes in response to graded levels of dietary taurine supplementation. The analysis used proton nuclear magnetic resonance-based metabolomics. Four groups of tilapias were fed with four diets supplemented with 0.0, 0.4, 0.8 and 1.2% taurine for 84 days. Fish plasma was sampled at multiple time points to provide an accurate snapshot of specific metabolic profiles during growth. Under the effect of taurine supplementation, 21 and 12 metabolites in tilapia plasma shown significant changes in terms of time-dependence and diet-dependence, respectively. These metabolic changes in tilapia plasma were mainly associated with energy and amino acid metabolism, lipids, nucleotides and protein metabolism. The results indicate that 0.8% taurine supplementation could significantly improve the carbohydrate synthesis, protein digestion and absorption, and fat deposition of tilapia and thereby promoted growth and development of tilapia.

Schizophyllum commune A alpha mating-type proteins, Y and Z, form complexes in all combinations in vitro.

Tha A alpha locus of the basidiomycete fungus, Schizophyllum commune, regulates sexual development via proteins Y and Z. Each A alpha mating type encodes unique Y and Z isoforms. We used two isoforms of Y (Y4 and Y5) and two isoforms of Z (Z4 and Z5) in affinity assays of protein binding. These assays identified two types of protein interactions. Each full-length Y or Z protein binds to itself and other Y or Z proteins regardless of the A alpha mating type from which they are encoded (i.e., mating-type independent binding). A second type of binding, detected with partial-length polypeptides, occurs only between N-terminal regions of Y and Z proteins encoded from different A alpha mating types (e.g., Y4Z5 or Y5Z4); we refer to this binding as mating-type dependent binding. Deletion analysis shows that the Y4 specificity domain (an N-terminal region conferring recognition uniqueness to the Y4 isoform) is essential for mating-type dependent binding. Other regions of Y and Z are involved in mating-type independent binding. These results, obtained in vitro, raise the possibility that either of several protein complexes composed of Y and/or Z proteins may occur in vivo.

Expression of the oxidative base excision repair enzymes is not induced in TK6 human lymphoblastoid cells after low doses of ionizing radiation.

Most of the DNA damage produced by ionizing radiation is repaired by the base excision repair (BER) pathway. To determine whether the BER genes were up-regulated by low doses of ionizing radiation, we investigated their expression in TK6 human lymphoblastoid cells by measuring mRNA levels using real-time quantitative PCR. No induction at the transcriptional level of any of the base excision repair genes, NTH1 (NTHL1), OGG1, NEIL1, NEIL2, NEIL3, APE1, POLB, or accessory protein genes, LIG3, XRCC1 or XPG, was found at gamma-radiation doses ranging from 1 cGy to 2 Gy in a 24-h period. As has been measured in other cell lines, a dose-dependent induction of CDKN1A (WAF1) mRNA levels was observed in TK6 cells in the dose range of 0.5 to 2.0 Gy. We also examined BER enzyme activity on 8-oxoguanine-, dihydrouracil- and furan-containing oligonucleotide substrates and found no increase in extracts of TK6 cells after gamma-ray doses of 0.5-2.0 Gy. These data were corroborated by Western blot analysis of APE1 and NTH1, suggesting that the BER enzymes are also not up-regulated at the post-transcriptional level after ionizing radiation exposure.

The A alpha mating-type transcripts of Schizophyllum commune.

A alpha 1, A alpha 3, and A alpha 4 ds- and ss-DNA probes from the polymorphic A alpha mating-type locus of Schizophyllum commune were used to probe Northern blots of poly(A+) RNA extracted from strains of various A alpha mating types. The purpose of these experiments was to identify, map, and characterize the transcripts produced from the regions of the A alpha locus. The transcripts unique to A alpha mating type map colinear with the open reading frames identified from DNA sequence and are encoded within the fragments which activate the A developmental pathway in transformation. These data confirm the existence and structure of the previously hypothesized Y and Z A alpha mating-type genes. Transcripts from the Y and Z genes are present in vegetative cells of homokaryons and dikaryons and in cells of the fruiting bodies. The presence of the transcripts throughout the life cycle is consistent with the model of Y and Z proteins as "master switches" of A-regulated development.

Cloning and characterization of a Schizophyllum gene with A beta 6 mating-type activity.

The A-pathway of development in the basidiomycete fungus Schizophyllum commune may be activated by either of two mating-type loci, A alpha and A beta. A alpha consists of two multiallelic genes, Y and Z. Y contains a putative homeodomain; Z contains a homeodomain-related region. Non-self combinations of Y and Z form heteromultimers which are thought to be transcription factors of developmental genes. To more completely understand A-regulated development it is necessary to address the issue of functional redundancy, i.e., how do two different mating loci, A alpha and A beta, both manage to regulate the same pathway. Here we report the structure of a gene with A beta 6 activity. This gene, denoted A beta V6, encodes a deduced polypeptide of 640 amino-acids with a homeodomain motif. V6 also contains a 20-amino acid sequence that is conserved in A alpha Y1, Y3 and Y4. Except for the homeodomain and the conserved sequence, the deduced V6 polypeptide shows no significant identity to A alpha Y, A alpha Z, or other known proteins. The presence of a homeodomain suggests that V, like Y and Z, may be a regulatory protein for genes in the A-pathway. Thus while A alpha and A beta encode different proteins, the general mechanism by which A alpha and A beta components signal A-regulated development may be similar.

The Aalpha6 locus: its relation to mating-type regulation of sexual development in Schizophyllum commune.

We have isolated and examined the Aalpha6 mating-type locus of Schizophyllum commune as a first step toward resolving a functional difference between this locus and the Aalpha loci previously studied. Our analyses show Aalpha6 to be remarkably similar to the Aalpha loci of known structure. The locus is composed of two, divergently transcribed genes similar in size to known Z and Y genes of the Aalpha loci. We have termed the two genes, Z6 and Y6, on the basis of their demonstrated mating activities and encoded protein motifs. The Z6 gene encodes a homeodomain-related sequence, two acidic regions and a predicted coiled-coil motif. The Y6 gene encodes a homeodomain, predicted coiled-coil motif, two regions with homology to the Abeta locus gene V6, a basic region encoding a putative nuclear localization sequence and a serine-rich region. The Z6 and Y6 proteins share these features with the other known Z and Y proteins, respectively. One of the two amino acid sequences with homology to the AbetaV6 protein has not previously been reported.

Mammalian mitochondrial intermediate peptidase: structure/function analysis of a new homologue from Schizophyllum commune and relationship to thimet oligopeptidases.

Mitochondrial intermediate peptidase (MIP) is a component of the mitochondrial protein import machinery required for maturation of nuclear-encoded precursor proteins targeted to the mitochondrial matrix or inner membrane. We previously characterized this enzyme in rat (RMIP) and Saccharomyces cerevisiae (YMIP) and showed that MIP activity is essential for mitochondrial function in yeast. We have now defined the structure of a new MIP homologue (SMIP) from the basidiomycete fungus Schizophyllum commune. SMIP includes 4 exons of 523, 486, 660, and 629 bp separated by 3 short introns. The predicted SMIP, YMIP, and RMIP sequences share 31-37% identity and 54-57% similarity over 700 amino acids. When SMIP and RMIP were expressed in a yeast mip1 delta mutant, they were both able to rescue the respiratory-deficient phenotype caused by genetic inactivation of YMIP, indicating that the function of this enzyme is conserved in eukaryotes. Moreover, the MIP sequences show 20-24% identity and 40-47% similarity to a family of oligopeptidases from bacteria, yeast, and mammals. MIP and these proteins are characterized by a highly conserved motif, F-H-E-X-G-H-(X)2-H-(X)12-G-(X)5-D-(X)2-E-X-P-S-(X)3-E-X, centered around a zinc-binding site and appear to represent a new family of genes associated with proteolytic processing in the mitochondrial and cytosolic compartments.