No abstract

Abstract. The PML protein was first identified as part of a fusion product with the retinoic acid receptor (RARa), resulting from the t(15;17) chromosomal translocation associated with acute promyelocytic leukemia (APL). It has been previously demonstrated that PML, which is tightly bound to the nuclear matrix, concentrates in discrete subnuclear compartments that are disorganized in APL cells due to the expression of the PML-RARa hybrid. Here we report that adenovirus infection causes a drastic redistribution of PML from spherical nuclear bodies into fibrous structures. The product encoded by adenovirus E4-ORF3 is shown to be responsible for this reorganization and to colocalize with PML into these fibers. In addition, we demonstrate that E1A oncoproteins concentrate in the PML domains, both in infected and transiently transfected cells, and that this association requires the conserved amino acid motif (D)LXCXE, common to all viral oncoproteins that bind pRB or the related p107 and p130 proteins. The SV-40 large T antigen, another member of this oncoprotein family is also found in close association with the PML nuclear bodies. Taken together, the present data indicate that the subnuclear domains containing PML represent a preferential target for DNA tumor viruses, and therefore suggest a more general involvement of the PML nuclear bodies in oncogenic processes.T HE eukaryotic nucleus is highly organized into discrete domains which spatially separate different biochemical processes. A variety of metabolic activities such as DNA replication, ribosome assembly, transcription, and pre-mRNA processing localize to distinct subnuclear compartments. The most conspicuous example is the nucleolus in which rRNAs are assembled into ribosomal subunits (reviewed by Scheer and Weisenberger, 1994). DNA replication sites were also shown to concentrate within discrete regions containing the proliferating cell nuclear antigen (PCNA; 1 Bravo and MacdonaldBravo, 1987) as well as DNA methyltransferase (Leonhardt et al., 1992). In addition, the small nuclear ribonucleoprotein particles (snRNPs), which are the major subunits of spliceosomes, were similarly found to localize to T. Carvalho and J.-S. Seeler should be considered as first authors.

In the nucleus of higher eukaryotes, maturation of mRNA precursors involves an orderly sequence of transcription-coupled interdependent steps. Transcription is well known to influence splicing, but how splicing may affect transcription remains unclear. Here we show that a splicing mutation that prevents recruitment of spliceosomal snRNPs to nascent transcripts causes co-transcriptional retention of unprocessed RNAs that remain associated with polymerases stalled predominantly at the 3' end of the gene. In contrast, treatment with spliceostatin A, which allows early spliceosome formation but destabilizes subsequent assembly of the catalytic complex, abolishes 3' end pausing of polymerases and induces leakage of unspliced transcripts to the nucleoplasm. Taken together, the data suggest that recruitment of splicing factors and correct assembly of the spliceosome are coupled to transcription termination, and this might ensure a proofreading mechanism that slows down release of unprocessed transcripts from the transcription site.

How splicing factors are recruited to nascent transcripts in the nucleus in order to assemble spliceosomes on newly synthesised pre-mRNAs is unknown. To address this question, we compared the intranuclear trafficking kinetics of small nuclear ribonucleoprotein particles (snRNP) and non-snRNP proteins in the presence and absence of splicing activity. Photobleaching experiments clearly show that spliceosomal proteins move continuously throughout the entire nucleus independently of ongoing transcription or splicing. Using quantitative experimental data, a mathematical model was applied for spliceosome assembly and recycling in the nucleus. The model assumes that splicing proteins move by Brownian diffusion and interact stochastically with binding sites located at different subnuclear compartments. Inhibition of splicing, which reduces the number of pre-mRNA binding sites available for spliceosome assembly, was modeled as a decrease in the on-rate binding constant in the nucleoplasm. Simulation of microscopy experiments before and after splicing inhibition yielded results consistent with the experimental observations. Taken together, our data argue against the view that spliceosomal components are stored in nuclear speckles until a signal triggers their recruitment to nascent transcripts. Rather, the results suggest that splicing proteins are constantly diffusing throughout the entire nucleus and collide randomly and transiently with pre-mRNAs.

A 5.4-kb cDNA encoding the protein that binds to the B Box of the plasminogen activator inhibitor-1 (PAI-1) gene was isolated and sequenced. The protein, named helicase-like transcription factor (HLTF), contains a DNA-binding domain, a RING finger domain, and seven helicase domains and is homologous to SWI/SNF proteins. Two HLTF mRNAs of 5.5 and 4.5 kb were detected in most human tissues, a single gene was located on chromosome 3q24-25, and the protein was located in the nucleoplasm. Two HLTF proteins differing in translation start site (Met-1 or Met-123) were obtained by in vitro translation in reticulocyte lysate or by immunoprecipitation from HeLa cell nuclear extracts. In vitro transcription from the PAI-1 promoter in HeLa cell extracts was inhibited by HLTF antibodies and by the HLTF DNA binding domain. Over-expression of HLTF or HLTFMet123 produced a three-fold induction of PAI-1-LUC transient expression in HeLa cells. Mutation of the PAI-1 B Box led to an eight-fold reduction of basal PAI-1-LUC expression in these cell lines, but did not affect the four- to six-fold induction by phorbol esters.

The spliceosomal snRNAs U1, U2, U4, and U5 are synthesized in the nucleus, exported to the cytoplasm to assemble with Sm proteins, and reimported to the nucleus as ribonucleoprotein particles. Recently, two novel proteins involved in biogenesis of small nuclear ribonucleoproteins (snRNPs) were identified, the Spinal muscular atrophy disease gene product (SMN) and its associated protein SIP1. It was previously reported that in HeLa cells, SMN and SIP1 form discrete foci located next to Cajal (coiled) bodies, the so-called “gemini of coiled bodies” or “gems.” An intriguing feature of gems is that they do not appear to contain snRNPs. Here we show that gems are present in a variable but small proportion of rapidly proliferating cells in culture. In the vast majority of cultured cells and in all primary neurons analyzed, SMN and SIP1 colocalize precisely with snRNPs in the Cajal body. The presence of SMN and SIP1 in Cajal bodies is confirmed by immunoelectron microscopy and by microinjection of antibodies that interfere with the integrity of the structure. The association of SMN with snRNPs and coilin persists during cell division, but at the end of mitosis there is a lag period between assembly of new Cajal bodies in the nucleus and detection of SMN in these structures, suggesting that SMN is targeted to preformed Cajal bodies. Finally, treatment of cells with leptomycin B (a drug that blocks export of U snRNAs to the cytoplasm and consequently import of new snRNPs into the nucleus) is shown to deplete snRNPs (but not SMN or SIP1) from the Cajal body. This suggests that snRNPs flow through the Cajal body during their biogenesis pathway.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• Pharmacokinetic interactions between albendazole and praziquantel are based on plasma concentrations of the enantiomeric mixture of both drugs with contradictory data, although the antiparasitic activity arises from (-)-(R)-praziquantel and (+)-albendazole sulfoxide. WHAT THIS STUDY ADDS• The pharmacokinetic interaction between albendazole and praziquantel is enantioselective. Praziquantel increased the plasma concentrations of (+)-albendazole sulfoxide more than those of (-)-albendazole sulfoxide and the administration of albendazole did not change the kinetic disposition of (+)-(S)-praziquantel, but increased the plasma concentration of (-)-(R)-praziquantel. AIMThis study investigated the kinetic disposition, metabolism and enantioselectivity of albendazole (ABZ) and praziquantel (PZQ) administered alone and in combination to healthy volunteers. METHODSA randomized crossover study was carried out in three phases (n = 9), in which some volunteers started in phase 1 (400 mg ABZ), others in phase 2 (1500 mg PZQ), and the remaining volunteers in phase 3 (400 mg ABZ + 1500 mg PZQ). Serial blood samples were collected from 0-48 h after drug administration. Pharmacokinetic parameters were calculated using a monocompartmental model with lag time and were analyzed using the Wilcoxon test; P Յ 0.05. RESULTSThe administration of PZQ increased the plasma concentrations of (+)-ASOX (albendazole sulphoxide) by 264% (AUC 0.99 vs. 2.59 mg ml -1 h), (-)-ASOX by 358% (0.14 vs. 0.50 mg ml -1 h) and albendazole sulfone (ASON) by 187% (0.17 vs. 0.32 mg ml -1 h). The administration of ABZ did not change the kinetic disposition of (+)-(S)-PZQ (-)-(R)-4-OHPZQ or (+)-(S)-4-OHPZQ, but increased the plasma concentration of (-)-(R)-PZQ by 64.77% (AUC 0.52 vs. 0.86 mg ml -1 h). CONCLUSIONSThe pharmacokinetic interaction between ABZ and PZQ in healthy volunteers was demonstrated by the observation of increased plasma concentrations of ASON, both ASOX enantiomers and (-)-(R)-PZQ. Clinically, the combination of ABZ and PZQ may improve the therapeutic efficacy as a consequence of higher concentration of both active drugs. On the other hand, the magnitude of this elevation may represent an increased risk of side effects, requiring, certainly, reduction of the dosage. However, further studies are necessary to evaluate the efficacy and safety of this combination.

W e present a case of recurrent auricular chondritis, which developed after two injections of a luteinising hormone-releasing hormone (LH-RH) analogue buserelin combined with oral treatment of a pure antiandrogen bicalutamide (Casodex). The patient was treated successfully with a continuous moderate dose of corticosteroids together with azathioprine and methotrexate. Complete repair of the deformed ear followed 7 months after starting the treatment.Relapsing polychondritis (RP) is a chronic autoimmune cartilaginous inflammation. Auricular chondritis is a presenting sign in over 85% of patients, in which patients' ears become red, swollen, and tender. We observed a painless form of recurrent auricular chondritis complicated by severe cartilage damage. CASE REPORTA 69 year old man had a history of old myocardial infarction and prostatic adenocarcinoma (Gleason score VI, stage T2B NO MO). He underwent two injections of an LH-RH analogue buserelin (Suprefact Depot, Aventis Pharma), combined with a pure antiandrogen bicalutamide (Casodex; AstraZeneca).Five months after starting treatment he presented with a painless redness and swelling of his right ear, which spared the lobe. This inflammation, showing inflammatory mononuclear infiltrate, progressed to include dropping and deformity of the upper part of the ear, and resolved spontaneously after 3 months (figs 1A and 2). The patient was then referred to the rheumatologist.Besides the dropped pinna, no systemic manifestations were found on physical examination and the patient's neurological status was unremarkable, including normal pain perception. Retinal screening showed no vasculitic changes. Routine laboratory investigation was normal except for raised inflammatory markers: erythrocyte sedimentation rate and C reactive protein. Serum immunoelectrophoresis, antinuclear antibodies, antineutrophil cytoplasmic antibodies, rheumatoid factor, prostate-specific antigen were normal. Viral serology, tuberculin test, and Venereal Disease research Laboratory test were negative. Ultrasound of large vessels and echocardiography were normal. A chest x ray examination and computed tomography (CT), abdominal CT, and bone scan were unremarkable.Owing to serious coronary disease, the lack of active auricular inflammation and systemic disease, and because buserelin treatment had been stopped, it was decided to observe the patient without treatment. However, painless auricular chondritis of the opposite side occurred 3 months later, supporting an initial suspicion of relapsing polychondritis. Prednisone 40 mg/day and azathioprine 100 mg/day were given. Corticosteroids were tapered to 20 mg/day for 1 month after reduction of inflammation in the opposite ear. Azathioprine treatment was stopped when the liver enzyme level was significantly raised after 2 months of treatment. A daily dose of prednisone 20 mg/day was continued, and oral methotrexate 7.5 mg/week was started after the liver function returned to normal. Partial repair of the auricular cartilage was noted 2 months later and f...