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Biomedical subjects

G Meister

Publications and source records attributed to G Meister.

At least 19 recordsLinked to original sources

Methylation of Sm proteins by a complex containing PRMT5 and the putative U snRNP assembly factor pICln.

Seven Sm proteins, termed B/B', D1, D2, D3, E, F, and G, assemble in an ordered manner onto U snRNAs to form the Sm core of the spliceosomal snRNPs U1, U2, U4/U6, and U5. The survival of motor neuron (SMN) protein binds to Sm proteins and mediates in the context of a macromolecular (SMN-) complex the assembly of the Sm core. Binding of SMN to Sm proteins is enhanced by modification of specific arginine residues in the Sm proteins D1 and D3 to symmetrical dimethylarginines (sDMAs), suggesting that assembly might be regulated at the posttranslational level. Here we provide evidence that the previously described pICln-complex, consisting of Sm proteins, the methyltransferase PRMT5, pICln, and two novel factors, catalyzes the sDMA modification of Sm proteins. In vitro studies further revealed that the pICln complex inhibits the spontaneous assembly of Sm proteins onto a U snRNA. This effect is mediated by pICln via its binding to the Sm fold of Sm proteins, thereby preventing specific interactions between Sm proteins required for the formation of the Sm core. Our data suggest that the pICln complex regulates an early step in the assembly of U snRNPs, possibly the transfer of Sm proteins to the SMN-complex.

Animals↗

SMNrp is an essential pre-mRNA splicing factor required for the formation of the mature spliceosome.

SMNrp, also termed SPF30, has recently been identified in spliceosomes assembled in vitro. We have functionally characterized this protein and show that it is an essential splicing factor. We show that SMNrp is a 17S U2 snRNP-associated protein that appears in the pre-spliceosome (complex A) and the mature spliceosome (complex B) during splicing. Immunodepletion of SMNrp from nuclear extract inhibits the first step of pre-mRNA splicing by preventing the formation of complex B. Re-addition of recombinant SMNrp to immunodepleted extract reconstitutes both spliceosome formation and splicing. Mutations in two domains of SMNrp, although similarly deleterious for splicing, differed in their consequences on U2 snRNP binding, suggesting that SMNrp may also engage in interactions with splicing factors other than the U2 snRNP. In agreement with this, we present evidence for an additional interaction between SMNrp and the [U4/U6.U5] tri-snRNP. A candidate that may mediate this interaction, namely the U4/U6-90 kDa protein, has been identified. We suggest that SMNrp, as a U2 snRNP-associated protein, facilitates the recruitment of the [U4/U6.U5] tri-snRNP to the pre-spliceosome.

Animals↗

A multiprotein complex mediates the ATP-dependent assembly of spliceosomal U snRNPs.

The spliceosomal snRNPs U1, U2, U4 and U5 contain a common RNP structure termed the Sm core that is formed by the binding of Sm proteins onto the U snRNA. Although isolated Sm proteins assemble spontaneously onto U snRNAs in vitro, there is increasing evidence that SMN and its interactor Gemin2 are involved in this process in vivo. Here, we describe a cell-free assay system for the assembly of U snRNPs that closely reproduces in vivo conditions. Using this system, we show that assembly of U1 snRNP depends on ATP. Immunodepletion of SMN-Gemin2 from the extract abolished assembly even though the extract contained high levels of Sm proteins. An affinity-purified macromolecular SMN complex consisting of 16 components including all Sm proteins restored assembly in the immunodepleted extract. These data provide the first direct evidence that a complex containing SMN and Gemin2 mediates the active assembly of spliceosomal U snRNPs.

Adenosine Triphosphate↗

Characterization of a nuclear 20S complex containing the survival of motor neurons (SMN) protein and a specific subset of spliceosomal Sm proteins.

Spinal muscular atrophy (SMA) is a neurodegenerative disease of motor neurons caused by reduced levels of functional survival of motor neurons (SMN) protein. Cytoplasmic SMN directly interacts with spliceosomal Sm proteins and facilitates their assembly onto U snRNAs. Nuclear SMN, in contrast, mediates recycling of pre-mRNA splicing factors. In this study, we have addressed the function of SMN in the nucleus. We show that a monoclonal antibody directed against SMN inhibits pre-mRNA splicing. Interestingly, the mode of inhibition suggests a novel role for SMN in splicing that occurs prior to, or in addition to, its role in recycling. Using biochemical fractionation and anti-SMN immunoaffinity chromatography, we identified two distinct nuclear SMN complexes termed NSC1 and NSC2. The biochemical properties and protein composition of NSC1 were determined in detail. NSC1 migrates in sucrose gradients as a U snRNA-free 20S complex containing at least 10 proteins. In addition to SMN, these include the SMN-interacting protein 1 (SIP-1), the putative helicase dp103/Gemin3, the novel dp103/Gemin3-interacting protein GIP1/Gemin4 and three additional proteins with apparent masses of 43, 33 and 18 kDa, respectively. Most surprisingly, NSC1 also contains a specific subset of spliceosomal Sm proteins. This shows that the SMN-Sm protein interaction is not restricted to the cytoplasm. Our data imply that nuclear SMN affects splicing by modulating the Sm protein composition of U snRNPs.

Amino Acid Sequence↗

[Lipid intervention and coronary heart disease in men less than 56 years of age. The Coronary Intervention Study: CIS].

UNLABELLED: The CIS was undertaken with the aim to evaluate the effects of lipid modifications on angiographic progression and regression of CAD in patients with CAD and hypercholesterolemia. The design included a multicenter randomized, double-blind, parallel, placebo-controlled comparison, with target and safety limits for adjusting the trial medication depending on the LDL cholesterol level (LDL-C) achieved, i.e., up to 40 mg of simvastatin (S) or placebo (P) daily, add-on medication (up to 3 x 4 g Colestyramin), and diet counselling. Male patients, average age 49 (< or = 56) years, were included with angiographic CAD and a screening total cholesterol of 207-350 mg/dl, who were not due to undergo coronary bypass surgery or PTCA, who did not suffer from serious other disease (e.g., diabetes mellitus), and who had not undergone coronary bypass surgery previously. RESULTS: All baseline variables were comparable in the treatment groups, with 129 patients taking S and 125 taking P. Of these 254 patients 217 had their final study visit and 207 underwent a second angiography after an average treatment time of 2.3 years under an average daily dose of 37 mg S. 205 pairs of films were available for analysis. Vital information was obtained of all patients until closure of the data bank, half a year after the last study angiography. Five deaths occurred within the study period, 12 through March 15, 1995 (S: 1/6, P: 4/6). 37 patients (S: 18, P: 19) discontinued trial drug and protocol. Concomitant CAD medication was comparable in both groups, except lipid-lowering add-on medication which was significantly higher in the P group (38% versus 13%). Significant changes in lipid levels, on treatment, were observed in the S group amounting to a mean difference in LDL-C of -35%, in Apo-Protein B (ApoB) of -30%, in VLDL-C of -37%, and in triglycerides (TG) of -27%, and in HDL-C of +6%, in comparison to the control group; these differences were even greater in 137 fully compliant patients: -41, -36, -39, -31, and +7%, respectively. Progression in the S group was significantly less, as defined by the two primary target criteria: 1) the minimum obstruction diameter (MOD), determined by quantitative coronary angiography (QCA), decreased about five times less in comparison to the control group (S: by -0.017; P: -0.0954 mm), and 2) the standardized visual global change score (GCS) deteriorated almost three times less in the S group (by +0.20) than in the P group (+0.58). Of the secondary target criteria, the mean lumen diameter (QCA) also developed a significant difference (S: -0.20; P: +0.23 mm; p = 0.0006) with a trend toward regression in the S group. The QCA-%-stenosis deteriorated three- to four-times less in the S group as compared to the control group (S: by 0.69%; P: by 2.73%; p = 0.0022), and the number of patients with angiographic progression was nearly halved (S: 30%; P: 56%; p < 0.0000). These differences were determined by intention to treat analysis (ITT), and they were obtained in spite of lipid lowering add-on medication in 38% of the P patients; they turned out to be more pronounced in 137 fully compliant patients, in an analysis "as treated". The mean decrease in LDL-C serum level caused by S was significantly correlated to the decrease in progression, and multivariate regression analysis of both treatment groups identified LDL-C (or ApoB) and TG as independent predictors of progression. Progression appeared to be most pronounced in low and medium sized lesions, and the beneficial effect of lipid intervention dominated in lesions with 12-56% QCA stenosis severity. A small fraction of patients who suffered from exercise-induced angina, with ST-segment-depression at the beginning of the study, experienced a significant improvement under S as compared to P treatment. Although the study was not designed to show differences in clinical events, the combined number of all major cardiovascular events tended to be less frequent in the S than in the C gr

Anticholesteremic Agents↗

Biodegradation of N-methylmorpholine-N-oxide.

N-Methylmorpholine-N-oxide (NMMO) is capable of dissolving cellulose without any further addition of chemicals. The solution can be used to produce cellulosic staple fibres by pressing it through spinning jets into an aqueous spinning bath. Because of results from conventional biodegradation tests using non-adapted activated sludge, the solvent is generally considered being persistent. The object of the described work was to show, whether and how activated sludge can be adapted to N-methylmorpholine-N-oxide and whether it is possible to purify NMMO-containing wastewaters in conventional wastewater treatment plants. The experiments showed that the sludge can be adapted within about 15-20 days. Adapted sludge can degrade the substance itself and its most important metabolites to concentrations below their detection levels and retain this ability even during limited periods without solvent being present in the wastewater. The main requirement for a successful adaptation is a high sludge age. The degradation takes place in several steps. First, NMMO is reduced to N-methylmorpholine. The next step is a demethylation of N-methylmorpholine to morpholine. This step is crucial for the adaptation process. Once morpholine has been formed, the adaptation proceeds very quickly until none of the substances in question can be detected any longer. So the next step must be the cleavage of the morpholine ring structure.

Biodegradation, Environmental↗

[Online patent searching--rapid responses to critical questions].

Online searching in publically available patent files opens up interesting possibilities to provide a rapid response to critical questions. A computerized analysis of all patents of leading German pharmaceutical companies over the last decade in important indication areas is described. Supported by subsequent manual processing of individual patents it is shown that duplicate experiments on animals practically never occur.

Chemical Phenomena↗

Causes of death in lethal rat malaria.

The involvement of the brain, lungs and kidneys was studied in a lethal rat malaria. Lewis inbred rats were infected with Plasmodium berghei K173. The disease proved fatal within 10-14 days. Parasitaemia showed an increase of up to 43% parasitised red blood cells on Day 10 p.i. The haematocrit decreased from 50% to 12%. The systolic blood pressure dropped from 99 to 56 mmHg. The lactate dehydrogenase activity rose to 2,543 U/l. BUN and serum creatinine doubled during the course of the disease. The transaminases increased tenfold and the cholinesterase decreased from 943 U/l to 271 U/l. Morphologically the kidneys showed an immune complex glomerulo-nephritis with a normal tubulo-interstitial system. The brain, heart and lungs were normal by light microscopic examination. Marked anaemia and shock were the main causes of death in the above-mentioned specimen rat, showing that the course of the disease is significantly different from lethal infections in humans with Plasmodium falciparum who show severe pulmonary, renal and cerebral complications.

Animals↗

Control of an outbreak of mouse coccidiosis in a closed colony.

In 1979 severe coccidiosis occurred within a closed colony of C57bl/6J Bom mice. The coccidiosis caused diarrhoea, weight loss and deaths. Pathogenicity and response to chemotherapy were studied in experimentally infected Bor: CFW1 (SPF) mice. Histological and other studies indicated that infection was caused by more than 1 Eimeria species which have not yet been determined. Treatment with different anticoccidial drugs was unsuccessful, but use of 2 triazinone-derivatives (Bay g 7183, Bay i 9142) added to the food (15 ppm) succeeded in completely eradicating the organisms from the breeding houses. Experimental findings on the sensitivity of the coccidia to other anticoccidial drugs are described.

Animals↗

[A method to detect microfilariae of Dipetalonema witei in the peripheral blood of mastomys natalensis (author's transl)].

A new cheap and time saving procedure is described for the detection of microfilariae of Dipetalonema witei in the peripheral blood of Mastomys natalensis. A special apparatus delivering an ether-air mixture is used to anesthetize the experimental animals for a short period in a very careful way and without side effects. The ether wapour induces a rapid shift of microfilariae within one minute from the lung to the peripheral blood.

Anesthesia, Inhalation↗