Cryo-EM structure of the Mre11-Rad50-Nbs1 complex reveals the molecular mechanism of scaffolding functions.

The DNA double-strand break repair complex Mre11-Rad50-Nbs1 (MRN) detects and nucleolytically processes DNA ends, activates the ATM kinase, and tethers DNA at break sites. How MRN can act both as nuclease and scaffold protein is not well understood. The cryo-EM structure of MRN from Chaetomium thermophilum reveals a 2:2:1 complex with a single Nbs1 wrapping around the autoinhibited Mre11 nuclease dimer.

Molecular basis of human ATM kinase inhibition.

Human checkpoint kinase ataxia telangiectasia-mutated (ATM) plays a key role in initiation of the DNA damage response following DNA double-strand breaks. ATM inhibition is a promising approach in cancer therapy, but, so far, detailed insights into the binding modes of known ATM inhibitors have been hampered due to the lack of high-resolution ATM structures. Using cryo-EM, we have determined the structure of human ATM to an overall resolution sufficient to build a near-complete atomic model and identify two hitherto unknown zinc-binding motifs.

Antioxidants and resistance against oxidation of porcine LDL subfractions.

The objective of this study was to determine the level of antioxidants, the content of fatty acids and peroxidation products, and the resistance against oxidation of native porcine LDL1 and LDL2. There were no significant differences in the fatty acid distribution of both native low density lipoprotein (LDL) subfractions, which was similar to that of human LDL. The total amount of alpha- and gamma-tocopherol of pig LDL was significantly lower than in human LDL, and beta-carotene, lycopene, and retinyl esters were totally absent.

Effects of low- and high-density lipoproteins on the proliferation of human breast cancer cells in vitro: differences between hormone-dependent and hormone-independent cell lines.

The influence of low- and high-density lipoproteins on the proliferation of human breast cancer cells in culture was studied. We compared total cell number after incubation for 48 hr in culture medium containing or lacking plasma lipoproteins. Marked differences were found between hormone-dependent (MCF-7, T-47-D, ZR-75) and hormone-independent (MDA-MB-231, HBL-100) mammary tumor cell lines.

Influence of morphology and malignancy of three new human melanoma cell lines on the cyclooxygenase pathway.

Three newly established human melanoma cell lines (WU-BI, PN-JC, MJ-ZJ) of different morphology and different stage of malignancy were incubated with ionophore A23187 (2.5 to 40 microM) or arachidonic acid (AA, 6.25 to 100 microM).

Continuous monitoring of in vitro oxidation of human low density lipoprotein.

The kinetics of the oxidation of human low density lipoprotein (LDL) can be measured continuously by monitoring the change of the 234 nm diene absorption. The time-course shows three consecutive phases, a lag-phase during which the diene absorption increases only weakly, a propagation phase with a rapid increase of the diene absorption and finally a decomposition phase. The increase of the dienes is highly correlated with the increase of MDA or lipid hydroperoxides.

Interaction of lipoprotein Lp(a) and low density lipoprotein with glycosaminoglycans from human aorta.

The lipoprotein complexing activity of glycosaminoglycans (GAG) prepared from human aortas with lipoprotein Lp(a) in comparison to low density lipoproteins (LDL) was determined tubidimetrically in the presence of Ca++. In control experiments, purified chondroitin-6 sulfate and proteoglycans (PG) were used. Lp(a) exhibited approximately a threefold higher reactivity.

Interaction of various lipoproteins from normal and dyslipoproteinemic plasma with mouse peritoneal macrophages.

In this study we tried to elucidate the atherogenicity of various plasma lipoproteins with respect to their capability of foam cell formation. Mouse peritoneal macrophages (MPM) were incubated with increasing amounts of lipoproteins and the incorporation of 14C oleate into the cholesteryl ester fraction was followed. The results may be summarized as follows: freshly isolated Lp(a) behaves very similar to normal LDL causing no or little increase in CE formation in MPM.

Cholesterol esterification in mouse peritoneal macrophages in the presence of pathological human plasma lipoproteins.

Mouse peritoneal macrophages were incubated with abnormal lipoproteins (LP-X, HDL-E, VLDL-p, IDl-p and LDL-p) from a patient with secondary deficiency in phosphatidylcholine-sterol acyltransferase, or with phosphatidylcholine/cholesterol liposomes, and the stimulation of cholesteryl ester formation was studied. Acetylated low density lipoproteins served as a control. It was found that macrophages incubated with LP-X, the other pathological lipoproteins or with liposomes did not show an enhanced cholesterol esterification.