RNA-binding protein HuR mediates cytoprotection through stimulation of XIAP translation.

Expression of the intrinsic cellular caspase inhibitor XIAP is regulated primarily at the level of protein synthesis. The 5' untranslated region harbours an Internal Ribosome Entry Site (IRES) motif that supports cap-independent translation of XIAP mRNA during conditions of cellular stress. In this study, we show that the RNA-binding protein HuR, which is known to orchestrate an antiapoptotic cellular program, stimulates translation of XIAP mRNA through XIAP IRES. We further show that HuR binds to XIAP IRES in vitro and in vivo, and stimulates recruitment of the XIAP mRNA into polysomes. Importantly, protection from the apoptosis-inducing agent etoposide by overexpression of HuR requires the presence of XIAP, suggesting that HuR-mediated cytoprotection is partially executed through enhanced XIAP translation. Our data suggest that XIAP belongs to the HuR-regulated RNA operon of antiapoptotic genes, which, along with Bcl-2, Mcl-1 and ProTα, contributes to the regulation of cell survival.

Distribution of selected virulence genes and antibiotic resistance in Enterococcus species isolated from the South Nation River drainage basin, Ontario, Canada.

AIMS: Isolate and characterize water enterococci from the South Nation River drainage basin, an area dominated by agriculture. METHODS AND RESULTS: A total of 1558 enterococci were isolated from 204 water samples from the South Nation River obtained over a 3-year period. PCR was used to identify isolates to the species level and characterize them for carriage of 12 virulence determinants. Antibiotic resistance was evaluated phenotypically. Enterococcus faecalis (36·4%), Enterococcus faecium (9·3%) and Enterococcus durans (8·5%) were the major enterococci species isolated. Enterococci carrying more than two virulence determinants were more frequently detected in the summer (59·6%) than in other seasons (≤ 37·6%). Very few isolates (≤ 2·0%) were resistant to category I antibiotics ciprofloxacin and vancomycin. CONCLUSIONS: Comparison of major water enterococci species with major faecal enterococci species obtained from various host groups (human, domesticated mammals and birds, wildlife) in this drainage basin suggest that water enterococci may have varied faecal origins. The low level of antibiotic resistance among enterococci suggests that dispersion of antibiotic resistance via waterborne enterococci in this watershed is not significant. SIGNIFICANCE AND IMPACT OF THE STUDY: The data obtained in this study suggests that water enterococci in the SNR have a faecal origin and that their potential impact on public health regarding antibiotic resistance and virulence determinants is minimal.

Selective culture medium enhances survival of neuroblasts from postnatal rodent brain.

One of the major limitations to the study of the development of the nervous system in aneuploid mammalian embryos is that the aneuploid condition is usually lethal in utero. Liveborn aneuploid individuals often succumb rapidly because they have a constellation of malformations incompatible with postnatal survival. We have developed a selective tissue culture medium (D-val) which can be used with fetal calf serum or in a serum-free defined composition and which permits neuroblasts and glioblasts present in postnatal rodent (rat, mouse) brain to proliferate and differentiate in vitro. These cells contain D-amino acid oxidase, but fibroblasts do not. In this medium, fibroblasts cannot grow and are eliminated from the cultures without the use of deleterious compounds such as antimitotic or chemotherapeutic agents. With this medium, cultures containing neuroblasts can be established from normal rat and mouse brain as late as postnatal days 11-20. Cultures with significant numbers of proliferating cells can also be established from perinatal aneuploid mouse embryos, 'rescuing' the cells for further study.