A population-based series of 649 unselected incident cases of ovarian cancer diagnosed in Ontario, Canada, during 1995-96 was screened for germline mutations in BRCA1 and BRCA2. We specifically tested for 11 of the most commonly reported mutations in the two genes. Then, cases were assessed with the protein-truncation test (PTT) for exon 11 of BRCA1, with denaturing gradient gel electrophoresis for the remainder of BRCA1, and with PTT for exons 10 and 11 of BRCA2. No mutations were found in all 134 women with tumors of borderline histology. Among the 515 women with invasive cancers, we identified 60 mutations, 39 in BRCA1 and 21 in BRCA2. The total mutation frequency among women with invasive cancers, 11.7% (95% confidence interval [95%CI] 9.2%-14.8%), is higher than previous estimates. Hereditary ovarian cancers diagnosed at age <50 years were mostly (83%) due to BRCA1, whereas the majority (60%) of those diagnosed at age >60 years were due to BRCA2. Mutations were found in 19% of women reporting first-degree relatives with breast or ovarian cancer and in 6.5% of women with no affected first-degree relatives. Risks of ovarian, breast, and stomach cancers and leukemias/lymphomas were increased nine-, five-, six- and threefold, respectively, among first-degree relatives of cases carrying BRCA1 mutations, compared with relatives of noncarriers, and risk of colorectal cancer was increased threefold for relatives of cases carrying BRCA2 mutations. For carriers of BRCA1 mutations, the estimated penetrance by age 80 years was 36% for ovarian cancer and 68% for breast cancer. In breast-cancer risk for first-degree relatives, there was a strong trend according to mutation location along the coding sequence of BRCA1, with little evidence of increased risk for mutations in the 5' fifth, but 8.8-fold increased risk for mutations in the 3' fifth (95%CI 3.6-22.0), corresponding to a carrier penetrance of essentially 100%. Ovarian, colorectal, stomach, pancreatic, and prostate cancer occurred among first-degree relatives of carriers of BRCA2 mutations only when mutations were in the ovarian cancer-cluster region (OCCR) of exon 11, whereas an excess of breast cancer was seen when mutations were outside the OCCR. For cancers of all sites combined, the estimated penetrance of BRCA2 mutations was greater for males than for females, 53% versus 38%. Past studies may have underestimated the contribution of BRCA2 to ovarian cancer, because mutations in this gene cause predominantly late-onset cancer, and previous work has focused more on early-onset disease. If confirmed in future studies, the trend in breast-cancer penetrance, according to mutation location along the BRCA1 coding sequence, may have significant impact on treatment decisions for carriers of BRCA1-mutations. As well, BRCA2 mutations may prove to be a greater cause of cancer in male carriers than previously has been thought.

In this article, a mechanism of arsenite [As(III)] resistance through methylation and subsequent volatization is described. Heterologous expression of arsM from Rhodopseudomonas palustris was shown to confer As(III) resistance to an arsenic-sensitive strain of Escherichia coli. ArsM catalyzes the formation of a number of methylated intermediates from As(III), with trimethylarsine as the end product. The net result is loss of arsenic, from both the medium and the cells. Because ArsM homologues are widespread in nature, this microbial-mediated transformation is proposed to have an important impact on the global arsenic cycle.As(III) ͉ ArsM ͉ methylation A s genomes are sequenced, it is becoming clear that nearly all bacteria and archaea have arsenic-resistance (ars) operons that confer resistance to arsenite [As(III)] and arsenate [As(V)] (1). The widespread occurrence of ars genes reflects the fact that arsenic is a ubiquitous environmental toxic metal. In most cases, these operons encode transport proteins that extrude As(III) from cells. In eukaryotes, As(III) detoxification involves glutathionylation coupled to removal of the As(GS) 3 complex from the cytosol by ABC transporters, such as the Saccharomyces cerevisiae Ycf1p vacuolar pump (2) or mammalian biliary extrusion pump MRP2 (3). In many mammals, including humans, an alternate metabolic fate of As(III) is methylation in the liver, followed by urinary excretion of the methylated species (4). In the past, this process was considered a detoxification mechanism (5), but more recent data suggest that the methylation actually increases toxicity by producing the more toxic monomethylarsenite [MMA(III)] and dimethylarsenite [DMA(III)], calling into question whether the process is, in fact, a detoxification process (6). An enzyme (termed Cyt19 or As3MT) that catalyzes As(III)-S-adenosylmethyltransferase activity has been identified recently in rats and humans (7-9). The enzyme has been characterized in vitro, but its physiological role is unknown.Bacteria and fungi are known to produce volatile and toxic arsines (10) but the physiological roles of arsenic methylation in microorganisms are likewise unclear, and the biochemical basis is unknown. While examining microbial genomes, we identified large number of genes for bacterial and archaeal homologues of Cyt19. We have termed a subset of these genes arsM and their protein product ArsM (As(III) S-adenosylmethyltransferase). What sets these arsM genes apart from genes for other homologues is that they are each downstream of an arsR gene, encoding the archetypal arsenic-responsive transcriptional repressor that controls expression of ars operons (11), suggesting that these ArsMs evolved to confer arsenic resistance.The gene for the 283-residue ArsM (29,656 Da) (accession no. NP948900.1) was cloned from Rhodopseudomonas palustris and expressed in an arsenic-hypersensitive strain of Escherichia coli. As(III)-resistance cells in E. coli expressing recombinant arsM correlated with conversion of medium arsenic to the methy...

All living organisms have systems for arsenic detoxi¢cation. The common themes are (a) uptake of As(V) in the form of arsenate by phosphate transporters, (b) uptake of As(III) in the form of arsenite by aquaglyceroporins, (c) reduction of As(V) to As(III) by arsenate reductases, and (d) extrusion or sequestration of As(III). While the overall schemes for arsenic resistance are similar in prokaryotes and eukaryotes, some of the speci¢c proteins are the products of separate evolutionary pathways. ß 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.

The copA gene product, a putative copper-translocating P-type ATPase, has been shown to be involved in copper resistance in Escherichia coli. The copA gene was disrupted by insertion of a kanamycin gene through homologous recombination. The mutant strain was more sensitive to copper salts but not to salts of other metals, suggesting a role in copper homeostasis. The coppersensitive phenotype could be rescued by complementation by a plasmid carrying copA from E. coli or copB from Enterococcus hirae. Expression of copA was induced by salts of copper or silver but not zinc or cobalt. Everted membrane vesicles from cells expressing copA exhibited ATP-coupled accumulation of copper, presumably as Cu(I). The results indicate that CopA is a Cu(I)-translocating efflux pump that is similar to the copper pumps related to Menkes and Wilson diseases and provides a useful prokaryotic model for these human diseases.soft metal resistance ͉ Menkes ͉ Wilson disease

Purpose The purposes of this study were to estimate the reduction in risk of ovarian, fallopian tube, or peritoneal cancer in women with a BRCA1 or BRCA2 mutation after oophorectomy, by age of oophorectomy; to estimate the impact of prophylactic oophorectomy on all-cause mortality; and to estimate 5-year survival associated with clinically detected ovarian, occult, and peritoneal cancers diagnosed in the cohort. Patients and Methods Women with a BRCA1 or BRCA2 mutation were identified from an international registry; 5,783 women completed a baseline questionnaire and ≥ one follow-up questionnaires. Women were observed until either diagnosis of ovarian, fallopian tube, or peritoneal cancer, death, or date of most recent follow-up. Hazard ratios (HRs) for cancer incidence and all-cause mortality associated with oophorectomy were evaluated using time-dependent survival analyses. Results After an average follow-up period of 5.6 years, 186 women developed either ovarian (n = 132), fallopian (n = 22), or peritoneal (n = 32) cancer, of whom 68 have died. HR for ovarian, fallopian, or peritoneal cancer associated with bilateral oophorectomy was 0.20 (95% CI, 0.13 to 0.30; P < .001). Among women who had no history of cancer at baseline, HR for all-cause mortality to age 70 years associated with an oophorectomy was 0.23 (95% CI, 0.13 to 0.39; P < .001). Conclusion Preventive oophorectomy was associated with an 80% reduction in the risk of ovarian, fallopian tube, or peritoneal cancer in BRCA1 or BRCA2 carriers and a 77% reduction in all-cause mortality.