We have cloned and expressed the inducible form of prostaglandin (PG) E synthase from rat and characterized its regulation of expression in several tissues after in vivo lipopoylsaccharide (LPS) challenge. The rat PGE synthase is 80% identical to the human enzyme at the amino acid level and catalyzes the conversion of PGH(2) to PGE(2) when overexpressed in Chinese hamster ovary K1 (CHO-K1) cells. PGE synthase activity was measured using [(3)H]PGH(2) as substrate and stannous chloride to terminate the reaction and convert all unreacted unstable PGH(2) to PGF(2alpha) before high pressure liquid chromatography analysis. We assessed the induction of PGE synthase in tissues from Harlan Sprague-Dawley rats after LPS-induced pyresis in vivo. Rat PGE synthase was up-regulated at the mRNA level in lung, colon, brain, heart, testis, spleen, and seminal vesicles. Cyclooxygenase (COX)-2 and interleukin 1beta were also up-regulated in these tissues, although to different extents than PGE synthase. PGE synthase and COX-2 were also up-regulated to the greatest extent in a rat model of adjuvant-induced arthritis. The RNA induction of PGE synthase in lung and the adjuvant-treated paw correlated with a 3.8- and 16-fold induction of protein seen in these tissues by immunoblot analysis. Because PGE synthase is a member of the membrane-associated proteins in eicosanoid and glutathione metabolism (MAPEG) family, of which leukotriene (LT) C(4) synthase and 5-lipoxygenase-activating protein are also members, we tested the effect of LTC(4) and the 5-lipoxygenase-activating protein inhibitor MK-886 on PGE synthase activity. LTC(4) and MK-886 were found to inhibit the activity with IC(50) values of 1.2 and 3.2 microm, respectively. The results demonstrate that PGE synthase is up-regulated in vivo after LPS or adjuvant administration and suggest that this is a key enzyme involved in the formation of PGE(2) in COX-2-mediated inflammatory and pyretic responses.

BackgroundSubclassification of ovarian carcinomas can be used to guide treatment and determine prognosis. Germline and somatic mutations, loss of heterozygosity (LOH), and epigenetic events such as promoter hypermethylation can lead to decreased expression of BRCA1/2 in ovarian cancers. The mechanism of BRCA1/2 loss is a potential method of subclassifying high grade serous carcinomas.MethodsA consecutive series of 49 ovarian cancers was assessed for mutations status of BRCA1 and BRCA2, LOH at the BRCA1 and BRCA2 loci, methylation of the BRCA1 promoter, BRCA1, BRCA2, PTEN, and PIK3CA transcript levels, PIK3CA gene copy number, and BRCA1, p21, p53, and WT-1 immunohistochemistry.ResultsEighteen (37%) of the ovarian carcinomas had germline or somatic BRCA1 mutations, or epigenetic loss of BRCA1. All of these tumours were high-grade serous or undifferentiated type. None of the endometrioid (n = 5), clear cell (n = 4), or low grade serous (n = 2) carcinomas showed loss of BRCA1, whereas 47% of the 38 high-grade serous or undifferentiated carcinomas had loss of BRCA1. It was possible to distinguish high grade serous carcinomas with BRCA1 mutations from those with epigenetic BRCA1 loss: tumours with BRCA1 mutations typically had decreased PTEN mRNA levels while those with epigenetic loss of BRCA1 had copy number gain of PIK3CA. Overexpression of p53 with loss of p21 expression occurred significantly more frequently in high grade serous carcinomas with epigenetic loss of BRCA1, compared to high grade serous tumors without loss of BRCA1.ConclusionHigh grade serous carcinomas can be subclassified into three groups: BRCA1 loss (genetic), BRCA1 loss (epigenetic), and no BRCA1 loss. Tumors in these groups show distinct molecular alterations involving the PI3K/AKT and p53 pathways.

Although the Archaea exhibit an intriguing combination of bacterial-and eukaryotic-like features, it is not known how these prokaryotic cells segregate their chromosomes before the process of cell division. In the course of our analysis of the third replication origin in the archaeon Sulfolobus solfataricus, we identify and characterise sister chromatid junctions in this prokaryote. This pairing appears to be mediated by hemicatenane-like structures, and we provide evidence that these junctions persist in both replicating and postreplicative cells. These data, in conjunction with fluorescent in situ hybridisation analyses, suggest that Sulfolobus chromosomes have a significant period of postreplicative sister chromatid synapsis, a situation that is more reminiscent of eukaryotic than bacterial chromosome segregation mechanisms.

No abstract