SUMO modification of the DEAD box protein p68 modulates its transcriptional activity and promotes its interaction with HDAC1.

The nuclear protein p68 (also known as Ddx5) is a prototypic member of the 'DEAD box' family of RNA helicases, which has been shown to be abnormally expressed and modified in colorectal tumors and to function as an important transcriptional regulator. Here, we show that p68 is modified in vivo on a single site (K53) by the small ubiquitin-like modifier-2 (SUMO-2). We demonstrate that the SUMO E3 ligase PIAS1 interacts with p68 and enhances its SUMO modification in vivo. To determine the functional consequences of SUMO modification, we compared the transcriptional activity of p68 and a K53R mutant that could not be SUMO-modified. Our data show that SUMO modification enhances p68 transcriptional repression activity and inhibits the ability of p68 to function as a coactivator of p53. These findings may be explained by the ability of wild type, but not K53R p68, to alter the modification state of chromatin by recruitment of histone deacetylase 1 (HDAC1).

Overexpression and poly-ubiquitylation of the DEAD-box RNA helicase p68 in colorectal tumours.

The DEAD box RNA helicase, p68, is upregulated in exponentially growing cells and shows cell cycle-dependent changes in nuclear localization. Although some other DEAD box proteins have been implicated in cancer, there have been no reports of any link between p68 status and carcinogenesis. In the present study we have analysed specimens from 50 patients with colorectal adenocarcinomas, including cases in which an adenomatous polyp was also present, by immunohistochemistry and Western blotting. Our data indicate that p68 protein is consistently overexpressed in tumours as compared with matched normal tissue. Examination of the levels of p68 mRNA from both normal and tumour tissue showed no obvious specific increase in p68 mRNA levels in tumours nor any evidence of underlying mutations in the p68 coding region. Interestingly, however, the accumulated p68 appears to be poly-ubiquitylated, suggesting a possible defect in proteasome-mediated degradation in these tumours. This overexpression/ubiquitylation is observed in both pre-invasive and invasive lesions suggesting that the dysregulation of p68 expression occurs early during tumour development. Finally, we demonstrate that ubiquitylation of p68 occurs in cultured cells, thereby providing a model for the molecular analysis of this process and its potential role in tumorigenesis.

Mite predator responses to prey and predator-emitted stimuli.

We found that the searching behavior of two acarine predators,Amblyseius fallacis andPhytoseiulus macropilis, for prey,Tetranychus urticae, is affected by the following stimuli: (1) prey silk and associated feces, whose combined physical and chemical properties elicit reduction in the rate of predator movements and longer halts; (2) kairomone extracted from prey silk and associated feces, which, upon contact, elicits frequent predator return to prey-inhabited locales; and (3) predator-emitted marking pheromone, which elicits shorter duration of search in presearched prey locales. We also found that treatment of filter paper with prey kairomone or silk enhanced predator location of prey eggs, leading us to speculate that application of synthetic prey kairomone could be useful in pest management programs.

Neurological, cardiovascular and metabolic effects of mefloquine in healthy volunteers: a double-blind, placebo-controlled trial.

1. To assess neurological, cardiovascular, metabolic and other side-effects of mefloquine given in conventional prophylactic dose to healthy volunteers, a double-blind, randomized, placebo-controlled trial was conducted. In addition, the identity of the active drug was concealed until the end of the trial. 2. A total of 106 healthy adults were recruited, of whom 95 (mean age 24 years; 45% males) completed the full study protocol. 3. Subjects had a baseline assessment, received placebo as first dose, were randomized to mefloquine 250 mg or placebo weekly for 4 weeks starting a week later, and were reassessed after the 2nd and 4th active/placebo doses. Subjects kept a daily symptom diary from 2 weeks before until 2 weeks after the dosing period. 4. Plasma mefloquine assay suggested compliance in all 46 subjects allocated active treatment (week 5 mean +/- s.d.; 2.35 +/- 0.94 mumol l-1. Mefloquine did not alter calcium homoeostasis but produced a mean 0.5 mmol l-1 fall in serum glucose over the study period (P < 0.001) and relative hyperinsulinaemia. Symbol digit modalities, and digit forwards and backwards test scores, were similar in active and placebo groups across the three assessments, as were lying/standing blood pressure and high-tone hearing loss. Electrocardiographic QTc interval prolongation and diarrhoea were mild but transient side-effects of mefloquine (P < 0.01). Neurological symptoms were comparable in the two groups throughout the study. There was no evidence of drug toxicity in 11 subjects who withdrew. 5. Mefloquine prophylaxis does not appear to produce low-grade but debilitating neurological symptoms or to alter the results of sensitive tests of cerebral function. However, there may be situations in which mefloquine might contribute to hypoglycaemia and cardiac dysrhythmias.

Karyotypic aberrations of chromosomes 16 and 17 are related to survival in patients with breast cancer.

BACKGROUND: Breast cancer has a high incidence and associated mortality rate, yet little is known of the sequence of genetic events that underlie the clinical course. METHODS: The study was a comparative genomic hybridization analysis of 40 primary breast cancers with survival data at a mean of 8.4 years. RESULTS: The mean number of aberrations was 9.0, with a mean of 5.5 gains and 3.5 deletions per tumour. The most common aberrations were: gain of 1q (27 of 40), 8q (19 of 40) and 17q (13 of 40), and deletion of 17p (12 of 40) and 8p (11 of 40). These results are consistent with a distinctive pattern of large-scale (karyotypic) genetic change in primary breast cancer. CONCLUSION: The novel findings of this study were that only women who were disease-free had loss of 16q (E-cadherin) in association with a gain of 16p, and 17p13 (p53) loss combined with 17q12 (HER2) amplification was found only in the cancers of women who developed recurrent disease. The karyotypic changes seen in primary breast cancer seem to be associated with outcome and point to the underlying genetic events.