SummaryZymocin-induced cell death in Saccharomyces cerevisiae requires the toxin-target (TOT) effector Elongator, a protein complex with functions in transcription, exocytosis and tRNA modification. In line with the latter, trm9 ∆ ∆ ∆ ∆ cells lacking a tRNA methylase specific for wobble uridine (U 34 ) residues survive zymocin and in excess, the Trm9 substrate tRNA Glu copies zymocin protection of Elongator mutants. Phenotypes typical of a tot3/elp3 ∆ ∆ ∆ ∆ Elongator mutant are absent from trm9 ∆ ∆ ∆ ∆ cells but copied in a tot3 ∆ ∆ ∆ ∆ trm9 ∆ ∆ ∆ ∆ double mutant suggesting that Elongator acts upstream of Trm9. Consistent with Elongator-dependent tRNA modification being more important to mRNA decoding than Trm9, SUP4 and SOE1 tRNA suppressors are highly sensitive to loss of Elongator and tRNA U 34 hypomodification. As Trm9 overexpression counteracts the effect of high-copy tRNA Glu

The mutation cluster region (MCR) of adenomatous polyposis coli (APC) is located within the central part of the open reading frame, overlapping with the region encoding the 20 amino acid repeats (20R) that are beta-catenin-binding sites. Each mutation in the MCR leads to the synthesis of a truncated APC product expressed in a colorectal tumour. The MCR extends from the 3' border of the first 20R coding region to approximately the middle of the third 20R coding region, reflecting both positive and negative selections of the N- and C-terminal halves of the APC protein in colon cancer cells, respectively. In contrast, the second 20R escapes selection and can be either included or excluded from the truncated APC products found in colon cancer cells. To specify the functional outcome of the selection of the mutations, we investigated the beta-catenin binding capacity of the first three 20R in N-terminal APC fragments. We found in co-immunoprecipitation and intracellular co-localization experiments that the second 20R is lacking any beta-catenin binding activity. Similarly, we also show that the tumour-associated truncations abolish the interaction of beta-catenin with the third 20R. Thus, our data provide a functional definition of the MCR: the APC fragments typical of colon cancer are selected for the presence of a single functional 20R, the first one, and are therefore equivalent relative to beta-catenin binding.

Proteolytic but chitinase-deficient microbial cultures were isolated from shrimp shell waste and characterized. The most efficient isolate was found to be a mixed culture consisting of two Bacillus licheniformis strains, which were first determined microscopically and physiologically. Molecular characterization was carried out by sequencing the 16S rRNA gene of both strains. According to the residual protein and ash content, the chitin obtained by fermentation of such a mixed culture was found to be comparable to a commercially available, chemically processed product. However, the strikingly high viscosity (80 versus 10 mPa of the commercially available sample) indicates its superior quality. The two strains differed in colony morphology and in their secretion capabilities for degradative extracellular enzymes. Sequencing of the loci encoding amylase, cellulase, chitinases, and proteases, as well as the degS/degU operon, which is instrumental in the regulation of degradative enzymes, and the pga operon, which is responsible for polyglutamic acid production, revealed no differences. However, a frameshift mutation in chiA, encoding a chitinase, was validated for both strains, providing an explanation for the ascertained absence of chitinolytic activities and the concomitant possibility of producing highly viscous chitin in a fermentational deproteinization process.Chitin (a polysaccharide consisting of ␤-1,4-linked N-acetyl-D-glucosamine moieties) is the second most abundant biopolymer on earth; thus, it represents a nearly constant source of renewable raw material. Along with its deacetylated derivative chitosan, chitin recently has gained biotechnological significance, not only because of favorable pharmaceutical features, such as antimicrobial, anticholesterol, and antitumor activities, but also because of its potential for wastewater treatment, drug delivery, and wound healing and as a dietary fiber (26).Approximately 50 to 60% of the total weight of shellfish, such as shrimp, crab, and krill, consists of nonedible material, i.e., "heads" and exoskeletons rich in chitin but also protein, which form, on the one hand, major environmental pollutants as a result of uncontrolled dumping (12). On the other hand, however, due to their chemical composition (20 to 30% chitin, 20 to 40% protein, 30 to 60% minerals, and 0 to 14% lipids) and their actual availability from seafood industries, shrimp waste also constitutes the major source for chitin and chitosan production (21). Currently applied methods to purify and modify chitin from such material and to transform it to useful carbohydrate products involve harsh chemical treatments accompanied by uncontrollable hydrolysis and chemical modifications that eventually result in the formation of undesired by-products such as irregularly deacetylated polymers (33).Exploitation limits are mainly set by the purification costs, which mainly arise from removal of proteins and calcium carbonate by alternating acid and alkali treatment, ultimately resulting in large amounts of aque...

The naturally occurring isothiocyanate sulforaphane (SFN) from cruciferous vegetables is associated with growth inhibition of various cancer types, including colorectal cancer. Colorectal cancer is most frequently driven by hyperactive Wnt/β-catenin signaling. Here, we show that SFN treatment reduced growth of three unrelated colorectal cancer cell lines (SW480, DLD1 and HCT116) via induction of cell death and inhibition of proliferation. Importantly, SFN inhibits Wnt/β-catenin signaling in colorectal cancer cells as shown by inhibition of β-catenin-dependent luciferase reporters and repression of β-catenin target genes (AXIN2, LGR5). SFN inhibits Wnt signaling downstream of β-catenin degradation and induces the formation of nuclear β-catenin structures associated with closed chromatin. Co-expression of the transcription factors LEF1 or TCF4 prevented formation of these structures and rescued inhibition of Wnt/β-catenin signaling by SFN. Our findings provide a molecular basis explaining SFN effects in colorectal cancer cells and underline its potential for prevention and therapy of colorectal cancer.