Localisation of somatostatin and somatostatin receptors in benign and malignant ovarian tumours

Somatostatin has been identified as having anti-proliferative, anti-angiogenic and pro-apoptotic actions in many tumour systems, and these effects are mediated through a family of five transmembrane G-protein coupled SRIF receptors. Ovarian cancer is the commonest gynaecological malignancy in the UK and maintenance therapy is urgently required. Native somatostatin expression and its receptors sst1,2,3 and 5 were studied with immunohistochemistry in 63 malignant and 35 benign ovarian tumours of various histological types. Fifty-seven out of 63 (90%) of malignant and 26/35 (74%) benign tumours expressed somatostatin. Receptors sst1,2,3 and 5 were expressed variably in epithelial, vascular and stromal compartments for both benign and malignant tumours. Somatostatin was found to correlate significantly with stromal sst1 (P=0.008), epithelial sst1 (P<0.001), stromal sst2 (P=0.019), vascular sst2 (P=0.026), epithelial sst3 (P=0.026), stromal sst5 (P=0.013) and vascular sst5 (P=0.038). Increased expression of native somatostatin correlating with somatostatin receptors in malignant ovarian tumours raises the possibility that either synthetic somatostatin antagonists or receptor agonists may have therapeutic potential

Kinetic analysis of the interaction of Mos1 transposase with its inverted terminal repeats reveals new insight into the protein-DNA complex assembly.

International audienceTransposases are specific DNA-binding proteins that promote the mobility of discrete DNA segments. We used a combination of physicochemical approaches to describe the association of MOS1 (an eukaryotic transposase) with its specific target DNA, an event corresponding to the first steps of the transposition cycle. Because the kinetic constants of the reaction are still unknown, we aimed to determine them by using quartz crystal microbalance on two sources of recombinant MOS1: one produced in insect cells and the other produced in bacteria. The prokaryotic-expressed MOS1 showed no cooperativity and displayed a Kd of about 300 nM. In contrast, the eukaryotic-expressed MOS1 generated a cooperative system, with a lower Kd (∼ 2 nm). The origins of these differences were investigated by IR spectroscopy and AFM imaging. Both support the conclusion that prokaryotic- and eukaryotic-expressed MOS1 are not similarly folded, thereby resulting in differences in the early steps of transposition

Calix[6]tren and copper(II): A third generation of funnel complexes on the way to redox calix-zymes

Mono-copper enzymes play an important role in biology and their functionality is based on Cu(II)/Cu(I) redox processes. Modeling a mono-nuclear site remains a challenge for a better understanding of its intrinsic reactivity. The first member of a third generation of calixarene-based mono-copper “funnel” complexes is described. The ligand is a calix[6]arene capped by a tren unit, hence presenting a N(4) coordination site confined in a cavity. Its Cu(II) complexes were characterized by electronic and EPR spectroscopies. The x-ray structure of one of them shows a five-coordinated metal ion in a slightly distorted trigonal bipyramidal geometry thanks to its coordination to a guest ligand L (ethanol). The latter sits in the heart of the hydrophobic calixarene cone that mimics the active site chamber and the hydrophobic access channel of enzymes. Competitive binding experiments showed a preference order dimethylformamide > ethanol > MeCN for L binding at the single exchangeable metal site. Cyclic voltammetry studies showed irreversible redox processes in CH(2)Cl(2) when L is an oxygen donor caused by the redox-driven ejection of the guest at the Cu(I) level. In the presence of MeCN, a pseudoreversible process was obtained, owing to a fast equilibrium between a fourand a five-coordinate Cu(I) species. Finally, a redox-driven ligand interchange of dimethylformamide for MeCN at the Cu(I) state allowed the trapping of the thermodynamically less stable Cu(II)-MeCN adduct. Hence, this work represents an important step toward the elaboration of a functional supramolecular model for redox mono-copper enzymes, named redox calix-zymes

Subunit architecture of general transcription factor TFIIH

Structures of complete 10-subunit yeast TFIIH and of a nested set of subcomplexes, containing 5, 6, and 7 subunits, have been determined by electron microscopy (EM) and 3D reconstruction. Consistency among all the structures establishes the location of the “minimal core” subunits (Ssl1, Tfb1, Tfb2, Tfb4, and Tfb5), and additional densities can be specifically attributed to Rad3, Ssl2, and the TFIIK trimer. These results can be further interpreted by placement of previous X-ray structures into the additional densities to give a preliminary picture of the RNA polymerase II preinitiation complex. In this picture, the key catalytic components of TFIIH, the Ssl2 ATPase/helicase and the Kin28 protein kinase are in proximity to their targets, downstream promoter DNA and the RNA polymerase C-terminal domain.National Cancer Institute (U.S.) (Grant number F32DK080622