Toxic DNA-protein crosslinks (DPCs) arise by ionizing irradiation and UV light, are particularly caused by endogenously produced reactive compounds such as formaldehyde, and also occur during compromised topoisomerase action. Although nucleotide excision repair and homologous recombination contribute to cell survival upon DPCs, hardly anything is known about mechanisms that target the protein component of DPCs directly. Here, we identify the metalloprotease Wss1 as being crucial for cell survival upon exposure to formaldehyde and topoisomerase 1-dependent DNA damage. Yeast mutants lacking Wss1 accumulate DPCs and exhibit gross chromosomal rearrangements. Notably, in vitro assays indicate that substrates such as topoisomerase 1 are processed by the metalloprotease directly and in a DNA-dependent manner. Thus, our data suggest that Wss1 contributes to survival of DPC-harboring cells by acting on DPCs proteolytically. We propose that DPC proteolysis enables repair of these unique lesions via downstream canonical DNA repair pathways.

Phenotypic characterization of the Arabidopsis thaliana transparent testa12 (tt12) mutant encoding a membrane protein of the multidrug and toxic efflux transporter family, suggested that TT12 is involved in the vacuolar accumulation of proanthocyanidin precursors in the seed. Metabolite analysis in tt12 seeds reveals an absence of flavan-3-ols and proanthocyanidins together with a reduction of the major flavonol quercetin-3-O-rhamnoside. The TT12 promoter is active in cells synthesizing proanthocyanidins. Using translational fusions between TT12 and green fluorescent protein, it is demonstrated that this transporter localizes to the tonoplast. Yeast vesicles expressing TT12 can transport the anthocyanin cyanidin-3-O-glucoside in the presence of MgATP but not the aglycones cyanidin and epicatechin. Inhibitor studies demonstrate that TT12 acts in vitro as a cyanidin-3-O-glucoside/H þ -antiporter. TT12 does not transport glycosylated flavonols and procyanidin dimers, and a direct transport activity for catechin-3-O-glucoside, a glucosylated flavan-3-ol, was not detectable. However, catechin-3-O-glucoside inhibited TT12-mediated transport of cyanidin-3-O-glucoside in a dose-dependent manner, while flavan-3-ol aglycones and glycosylated flavonols had no effect on anthocyanin transport. It is proposed that TT12 transports glycosylated flavan-3-ols in vivo. Mutant banyuls (ban) seeds accumulate anthocyanins instead of proanthocyanidins, yet the ban tt12 double mutant exhibits reduced anthocyanin accumulation, which supports the transport data suggesting that TT12 mediates anthocyanin transport in vitro.

On the basis of observations from Vitis vinifera cv. Pinotage wines and experiments performed in model wine medium, a new chemical pathway responsible for the formation of anthocyanin-vinylphenol adducts in red wines is described. Until now, these pigments have been considered to be reaction products of anthocyanins and vinylphenols, the latter being generated during fermentation by enzymatic decarboxylation of the respective cinnamic acids. The mechanism of the novel pathway, involving intact hydroxycinnamic acid and anthocyanin, is explained. Only cinnamic acids with electron-donating substituents on the aromatic ring, such as coumaric acid, ferulic acid, caffeic acid, and sinapic acid, undergo this conversion, as they stabilize an intermediately formed carbenium ion. Decarboxylation and oxidation of the pyran moieties are the final steps in the generation of the corresponding 4-vinylphenol, 4-vinylguaiacol, 4-vinylcatechol, and 4-vinylsyringol adducts of anthocyanins in red wine.

The prefermentation addition of copigments led to significantly different red wines according to the copigment structure (flavonol or hydroxycinnamic acid) and the grape cultivar [Tempranillo (= Cencibel) or Cabernet Sauvignon]. The flavonol rutin enhanced copigmentation and anthocyanin extraction, improving the red color, but the hydroxycinnamic acids (especially caffeic acid) had converse results. The above effects were higher in Cabernet Sauvignon wines, particularly if rutin or p-coumaric acid was used. These wines showed the highest copigmentation as they contained more anthocyanins and flavonols, whereas the coumaroylated anthocyanins of Tempranillo wines could have prevented the action of the added copigments. After 21 months, the main pyranoanthocyanins found were the malvidin-3-glucoside 4-vinylphenol and the malvidin-3-glucoside 4-vinylcatechol (pinotin A) adducts. The results suggested that the former adduct was primarily generated following enzymatic decarboxylation of p-coumaric acid during fermentation, whereas pinotin A was formed through a pure chemical reaction, which depended on the concentration of free caffeic acid during aging.

Anthocyanins are dietary flavonoids, which can prevent carcinogen-induced colorectal cancer in rats. Here, the hypotheses were tested that Mirtoselect, an anthocyanin mixture from bilberry, or isolated cyanidin-3-glucoside (C3G), the most abundant anthocyanin in diet, interfere with intestinal adenoma formation in the Apc Min mouse, a genetic model of human familial adenomatous polyposis, and that consumption of C3G or Mirtoselect generates measurable levels of anthocyanins in the murine biophase. Apc Min mice ingested C3G or Mirtoselect at 0.03, 0.1 or 0.3% in the diet for 12 weeks, and intestinal adenomas were counted. Plasma, urine and intestinal mucosa were analyzed for presence of anthocyanins by high-pressure liquid chromatography with detection by UV spectrophotometry (520 nm) or tandem mass spectrometry (multiple reaction monitoring). Ingestion of either C3G or Mirtoselect reduced adenoma load dose-dependently. At the highest doses of C3G and Mirtoselect adenoma numbers were decreased by 45% (p < 0.001) or 30% (p < 0.05), respectively, compared to controls. Anthocyanins were found at the analytical detection limit in the plasma and at quantifiable levels in the intestinal mucosa and urine. Anthocyanin glucuronide and methyl metabolites were identified in intestine and urine. Total anthocyanin levels in mice on C3G or Mirtoselect were 43 ng and 8.1 lg/g tissue, respectively, in the intestinal mucosa, and 7.2 and 12.3 lg/ml in the urine. The efficacy of C3G and Mirtoselect in the Apc Min mouse renders the further development of anthocyanins as potential human colorectal cancer chemopreventive agents worthwhile. ' 2006 Wiley-Liss, Inc. Key words: colorectal cancer chemoprevention; anthocyanin; analysisThere is an increasing interest in the role of dietary constituents in the prevention of cancer. Examples of dietary components, which have been implicated as cancer chemopreventive agents, are flavonoids such as genistein from soya, quercetin from onions or apigenin from leafy vegetables.1 Dietary intake of these flavonoids is estimated to be within the range of 20-25 mg/day. Anthocyanins are flavonoids responsible for the bright blue and red colors of many fruits and berries. They are glycosides of anthocyanidins, mainly cyanidin, delphinidin, malvidin, pelargonidin, peonidin and petunidin, conjugated with sugars, including glucose, galactose and arabinose (for structures see Fig. 1). The daily intake of anthocyanins in the US is in excess of 200 mg/day, amounts far superior to those of genistein or quercetin.3 Anthocyanins and anthocyanidins have demonstrated antiproliferative activity in some cancer cell lines with IC 50 values for growth inhibition in the range of 100-800 and 18-200 lM, respectively.4,5 Anthocyanins-and anthocyanin-rich fruit extracts decreased aberrant crypt foci in rats exposed to azoxymethane 6 and reduced colonic adenocarcinoma burden in rats that had received azoxymethane, 1,2-dimethylhydrazine or 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine.6-8 The Apc Min (multiple intestin...