Control of transfer RNA synthesis in the presence of inhibitors of protein synthesis

Synthesis of Trichodermin Derivatives and Their Antimicrobial and Cytotoxic Activities

Trichothecene mycotoxins are recognized as highly bioactive compounds that can be used in the design of new useful bioactive molecules. In Trichoderma brevicompactum, the first specific step in trichothecene biosynthesis is carried out by a terpene cyclase, trichodiene synthase, that catalyzes the conversion of farnesyl diphosphate to trichodiene and is encoded by the tri5 gene. Overexpression of tri5 resulted in increased levels of trichodermin, a trichothecene-type toxin, which is a valuable tool in preparing new molecules with a trichothecene skeleton. In this work, we developed the hemisynthesis of trichodermin and trichodermol derivatives in order to evaluate their antimicrobial and cytotoxic activities and to study the chemo-modulation of their bioactivity. Some derivatives with a short chain at the C-4 position displayed selective antimicrobial activity against Candida albicans and they showed MIC values similar to those displayed by trichodermin. It is important to highlight the cytotoxic selectivity observed for compounds 9, 13, and 15, which presented average IC₅₀ values of 2 μg/mL and were cytotoxic against tumorigenic cell line MCF-7 (breast carcinoma) and not against Fa2N4 (non-tumoral immortalized human hepatocytes).

Genome Sequence of Fusarium graminearum ITEM 124 (ATCC 56091), a Mycotoxigenic Plant Pathogen

Fusarium graminearum is among the main causal agents of Fusarium head blight (FHB), or scab, of wheat and other cereals, caused by a complex of Fusarium species, worldwide. Besides causing economic losses in terms of crop yield and quality, F. graminearum poses a severe threat to animal and human health. Here, we present the first draft whole-genome sequence of the mycotoxigenic Fusarium graminearum strain ITEM 124, also providing useful information for comparative genomics studies.

Relationship between mycoparasites lifestyles and biocontrol behaviors against Fusarium spp. and mycotoxins production

Global food security research is seeking eco-friendly solutions to control mycotoxins in grain infected by fungi (molds). In particular, mycotoxigenic Fusarium spp. outbreak is a chronic threat for cereal grain production, human, and animal health. In this review paper, we discuss up-to-date biological control strategies in applying mycoparasites as biological control agents (BCA) to prevent plant diseases in crops and mycotoxins in grain, food, and feed. The aim is to increase food safety and to minimize economic losses due to the reduced grain yield and quality. However, recent papers indicate that the study of the BCA specialists with biotrophic lifestyle lags behind our understanding of the BCA generalists with necrotrophic lifestyle. We examine critical behavioral traits of the two BCA groups of mycoparasites. The goal is to highlight their major characteristics in the context of future research towards an efficient biocontrol strategy against mycotoxin-producing Fusarium species. The emphasis is put on biocontrol of Fusarium graminearum, F. avenaceum, and F. culmorum causing Fusarium head blight (FHB) in cereals and their mycotoxins.

Proteome scale census of major facilitator superfamily transporters in Trichoderma reesei using protein sequence and structure based classification enhanced ranking

Trichoderma spp. have been acknowledged as potent bio-control agents against microbial pathogens and also as plant growth promoters. Various secondary metabolites are attributed for these beneficial activities. Major facilitator superfamily (MFS) includes the large proportion of efflux-pumps which are linked with membrane transport of these secondary metabolites. We have carried out a proteome-wide identification of MFS transporters using protein sequence and structure based hierarchical method in Trichoderma reesei. 448 proteins out of 9115 were detected to carry transmembrane helices. MFS specific intragenic gene duplication and its context with transport function have been presented. Finally, using homology based techniques, domains and motifs of MFS families have been identified and utilized to classify them. From query dataset of 448 transmembrane proteins, 148 proteins are identified as potential MFS transporters. Sugar porter, drug: H(+) antiporter-1, monocarboxylate porter and anion: cation symporter emerged as major MFS families with 51, 35, 17 and 11 members respectively. Representative protein tertiary structures of these families are homology modeled for structure-function analysis. This study may help to understand the molecular basis of secretion and transport of agriculturally valuable secondary metabolites produced by these bio-control fungal agents which may be exploited in future for enhancing its biotechnological applications in eco-friendly sustainable development.

A morpholino oligomer targeting highly conserved internal ribosome entry site sequence is able to inhibit multiple species of picornavirus

Members of the genera Enterovirus and Rhinovirus (family Picornaviridae) cause a wide range of human diseases. An established vaccine is available only for poliovirus, and no effective therapy is available for the treatment of infections caused by any pathogenic picornavirus. Peptide-conjugated phosphorodiamidate morpholino oligomers (PPMO) are single-stranded DNA-like antisense agents that readily enter cells. A panel of PPMO was tested for their antiviral activities against various picornaviruses. PPMO targeting conserved internal ribosome entry site (IRES) sequence were highly active against human rhinovirus type 14, coxsackievirus type B2, and poliovirus type 1 (PV1), reducing PV1 titers by up to 6 log(10) in cell cultures. Comparative sequence analysis led us to design a PPMO (EnteroX) targeting 22 nucleotides of IRES sequence that are perfectly conserved across greater than 99% of all human enteroviruses and rhinoviruses. EnteroX reduced PV1 replication in cell culture to an extent similar to that of other IRES-specific PPMO. Resistant PV1 arose in cell cultures after 12 passages in the presence of EnteroX and were found to have two mutations within the EnteroX target sequence. Nevertheless, cPVR transgenic mice treated once daily by intraperitoneal (i.p.) injection with EnteroX before and/or after i.p. infection with 3 x 10(8) PFU (three times the 50% lethal dose) of PV1 had an approximately 80% higher rate of survival than the controls. The viral titer in tissues taken at day 5 postinfection showed that animals in the EnteroX-treated group averaged over 3, 4, and 5 log(10) less virus in the small intestine, spinal cord, and brain, respectively, than the amount in the control animals. These results suggest that EnteroX may have broad therapeutic potential against entero- and rhinoviruses.

Differential effects of tri-n-butyltin chloride on macromolecular synthesis and ATP levels of rat thymocyte subpopulations obtained by centrifugal elutriation

Using centrifugal elutration, rat thymocytes were separated into three fractions by size. Fraction 1 (F1) consisted of a large population (greater than 88% of all cells) of small, nonproliferating thymocytes. Fraction 2 (F2; 7% of all cells) was enriched in medium-sized thymocytes and showed an increased macromolecular synthesis. In the small fraction 3 (F3; less than 5% of all cells), large thymocytes, monocytes, granulocytes and cells in mitosis were concentrated. F3 demonstrated the highest proliferative activity. Fractions were characterized by size, cell morphology, DNA, RNA and protein synthesis and steady state ATP levels. The effects of the inhibitor of oxidative phosphorylation, tri-n-butyltin chloride (TBTC) on ATP levels and the incorporation of DNA, RNA and protein precursors were investigated for each thymocyte fraction. Although ATP levels increased with increasing thymocyte volume, TBTC reduced ATP levels in each subfraction proportionally. The incorporation of thymidine and leucine was markedly reduced in all fractions by TBTC, but not to the same extend. Dependent on the TBTC concentration, the rapidly proliferating cells of F2 and F3 were less affected compared to the noncycling cells of F1. The incorporation of uridine in the unfractionated cells and in F2 and F3 was also decreased by TBTC. However, at concentrations between 0.1 and 1 microM, TBTC stimulated uridine incorporation in the small thymocytes of F1. Therefore, fractionation of thymocyte suspensions was necessary to detect differential effects of TBTC on subpopulations. Centrifugal elutriation was found to be a useful tool with which to obtain subfractions of isolated rat thymocytes.

The regulation of RNA synthesis in yeast. I: Starvation experiments

The synthesis of tRNA in yeast is shown to be under separate control to that of rRNA during amino acid and nitrogen starvation. Inhibitors of the elongation and termination steps of protein synthesis were found to stimulate the synthesis of tRNA in starved yeast cells. This effect appeared to be due to the "trickle-charging" of tRNA. Two inhibitors of early steps in the initiation of protein synthesis were found to be unable to stimulate RNA synthesis in starved cells. It is proposed that yeast tRNA synthesis is under autoregulatory control and that the level of tRNA charging and the mRNA-ribosome complex are important components of this control system.