Báo cáo khoa học: Symposia Lectures docx

Thursday, July 12, 2007 A5-L1 Systematic characterization of the protein interaction network for the human transcription machinery B. Coulombe 1 , C. Jeronimo 1 , D. Forget 1 , A. Bouchard 1 ,Q.Li 2 , G. Chua 3 , J. Greenblatt 3 , T. R. Hughes 3 , M. Blanchette 4 and D. Price 2 1 Institut de recherches cliniques de Montre ´ al, Montre ´ al, PQ, CANADA, 2 University of Iowa, Iowa City, IA, USA, 3 BBDMR, Toronto, ON, CANADA, 4 McGill Centre for Bioinformatics, Montre ´ al, PQ, CANADA We have performed a survey of soluble human protein complexes containing components of the transcription and RNA processing machineries using protein affinity purification coupled to mass spectrometry. Thirty-five tagged polypeptides yielded a network of 850 high-confidence interactions. Remarkably, the network is significantly enriched in proteins that regulate the formation of protein com- plexes, including a number of previously-uncharacterized proteins for which we have inferred functions. Among these newly-discovered proteins, the RNA polymerase II-associated proteins (RPAPs) are physically and functionally associated with RNA polymerase II, form- ing an interface between the enzyme and chaperone/scaffolding proteins. Another newly-discovered protein proved to be the long-awai- ted 7SK snRNA methylphosphate capping enzyme (MePCE). Our results indicate that MePCE is present in a novel snRNP complex containing both RNA processing and transcription factors, including the elongation factor P-TEFb. Our most recent findings addressing the function of the RPAPs and MePCE will be discussed. In summary, our results define a high-density protein interaction network for the mammalian transcription machinery and uncover multiple regulatory factors that target some of its key components. A5-L2 Coupling transcription with alternative splicing A. Kornblihtt, M. de la Mata, M. Munoz, M. Alle, S. Pancrez Santangelo, N. Rascovan and I. Schor Universidad de Buenos Aires, Buenos Aires, ARGENTINA Changes in RNA polymerase II (pol II) elongation rates affect the timing at which nascent pre-mRNA splice sites are presented to the spliceosome (kinetic coupling). On the other hand, interaction of splicing factors with pol II itself or with transcription factors may affect AS (recruitment coupling). To study the roles of pol II carboxy terminal domain (CTD) in AS we transfected cells with plasmids expressing WT or CTD-deleted pol II in conditions in which the endogenous enzyme is inhibited. CTD deletion causes higher inclusion of the fibronectin EDI alternative exon because the CTD-deleted pol II is unable to recruit the splicing factor SRp20 that acts as an inhibitor of EDI inclusion. In other series of experiments we show that DNA damage by UV-irradiation deeply affects AS of fibronectin and Bcl-x genes. This effect does not involve the p53 transcriptional activator, is independent of the damage in cis of the actual template and might be related to global changes in transcription that follow hyperphosphorylation of the pol II CTD. On the other hand, we investigated how changes in histone acetylation associated to neuronal plasticity affect AS of an NCAM (Neural Cell Adhesion Mole- cule) gene exon whose inclusion is modulated during long term potentiation. Symposia Lectures Thursday 56 A5-L3 snRNP and spliceosome assembly in vivo K. Neugebauer Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, GERMANY Pre-mRNA splicing is accomplished by the spliceosome, a macromolecular machine similar in size to the ribosome. The spliceosom- al snRNPs (U1, U2, U4, U5 and U6), consisting of small nuclear RNAs and specific proteins, can be thought of as sub-machines, which must themselves be assembled correctly in order to function within the spliceosome. I will discuss our recent evidence that a conserved subnuclear compartment, the Cajal body, is the site of snRNP assembly. Moreover, mathematical modeling shows that snRNP assembly in the CB increases the efficiency of particular steps in the pathway by 10-fold. Once assembled, snRNPs must participate in spliceosome assembly, which may occur independently on each intron destined for removal. In addition, because spli- cing occurs during the process of transcription, spliceosome assembly must be integrated with transcriptional events. We have devel- oped novel assays that allow for direct detection of snRNPs and other splicing factors in vivo along the lengths of active genes (‘splicing factor ChIP’) and this has permitted an analysis of co-transcriptional spliceosome assembly in yeast and human cells. We find that 5¢ end capping of nascent RNA is essential for proper spliceosome assembly and that transcriptional elongation rate can determine the extent to which RNA is co-transcriptionally spliced. A5-L4 Structural dynamics and function of the spliceosome R. Lu ¨ hrmann Max Planck Institute for Biophysical Chemistry, Go ¨ ttingen, GERMANY No abstract available. Thursday Symposia Lectures 57 A5-L5 mRNA quality control: an ancient machinery recognizes and degrades aberrant mRNAs E. Izaurralde Max Planck Institute for Developmental Biology, Tuebingen, GERMANY Nonsense-mediated mRNA decay (NMD) is a conserved mRNA quality control mechanism (surveillance) that ensures the fidelity of gene expression by detecting and degrading mRNAs containing premature translation termination codons (PTCs, nonsense co- dons). NMD safeguards cells from accumulating potentially deleterious truncated proteins. Our studies of the NMD pathway in Drosophila and human cells reveal that whilst the NMD machinery is conserved, different species have evolved different mechanisms of recognizing and degrading aberrant transcripts. These studies identified new components of the NMD machinery both in human and Drosophila cells. Once an aberrant mRNA is recognized by the NMD machinery, enzymes involved in general mRNA decay are recruited and the transcript is degraded rapidly. We have shown that SMG7, an essential NMD factor in human cells, provides the missing link between the NMD and the general cellular mRNA degradation machinery. To investigate the physiological role of NMD, we have analysed gene expression profiles in cells depleted of essential NMD factors. These studies showed that the NMD machinery not only degrades aberrant mRNAs containing nonsense codons caused by mutations, errors during transcription or RNA processing, but also plays an important role in the post-transcriptional regulation of a broad range of wild-type transcripts. B5-L1 The Meningococcal Transformation Machine T. Tonjum University of Oslo, Oslo, NORWAY No abstract available. Symposia Lectures Thursday 58 B5-L2 The protein export pathway for flagellum assembly on the bacterial cell surface C. Hughes University of Cambridge, Cambridge, UK A wide range of motile bacteria assemble flagella on their cell surface, facilitating cell swimming and population swarming in the envi- ronment and during colonisation of mammalian hosts. Our research focuses on the type III protein export pathway used to achieve ordered delivery of flagellar structural subunits from the cell cytosol to the nascent macromolecular structure. The flagellar export path- way comprises c.15 export proteins, and is closely related to that used by extracellular and intracellular pathogens to deliver subversive virulence effectors into human and animal cells during infection. Our work so far has revealed a number of key mechanistic activities and events in the pathway, including chaperone bodyguard function, membrane targeting and activation of the oligomeric export AT- Pase, chaperone piloting of subunits to the ATPase docking platform, and post-docking escort of unladen chaperones to establish a selective chaperone cycle. Our work and that of colleagues elsewhere allows us to outline a sequence of events, defined by transient pro- tein-protein interactions, that underlie piloting, docking, sorting, selection and release of subunits along the translocation pathway. References 1. Thomas J, Stafford GP, Hughes C. Docking of cytosolic chaperone-substrate complexes at the membrane ATPase during flagellar type III protein export. PNAS (USA) 2004; 101: 3945–3950. 2. Evans LD, Stafford GP, Ahmed S, Fraser GM, Hughes C. An escort mechanism for cycling of export chaperones during flagellum assembly. PNAS (USA) 2006; 103: 17474–9. B5-L3 Plasmodesmata: pathways for intercellular trafficking of macromolecules W. J. Lucas University of California, Davis, CA, USA Plasmodesmata (PD) establish a pathway for cell-to-cell communication within plant tissues and organs. Recent studies have demon- strated that PD evolved the capacity to mediate the cell-to-cell transport of macromolecules, including proteins and RNA. This gave rise to a system in which positional information could be delivered by non-cell-autonomously acting macromolecules, without pas- sage into the extracellular milieu. Initial insight into this unique function was gained through studies on viruses. Plant viruses encode non-structural proteins, termed movement proteins that function in the transport of viral infectious material through PD, thereby allowing the spread of infectious nucleic acids. These findings led to the discovery that many plant proteins, including tran- scription factors, are able to use this PD ‘cytoplasmic highway’ to traffic between cells. A number of these endogenous proteins have the capacity to potentiate the cell-to-cell transport of mRNA. Interestingly, proteins that can gain entry into the plant vascular system, and the phloem in particular, are able to move over long distances within the body of the plant. This special property of PD, to mediate the exchange of information molecules, led to the concept that higher plants function as supracellular organisms. Now that it has been unambiguously established that endogenous macromolecules have the capacity to function at a supracellular level, the challenge ahead is to identify the cellular components involved in both mediating and regulating this non-cell-autonomous protein translocation pathway. The focus of this talk will be on emerging principles of PD biology in areas of cell biology, develop- mental biology and inter-organ signaling. Acknowledgement Funding provided by NSF grant IBN 0444725 and DOE grant DE-FG03–94ER20134. Thursday Symposia Lectures 59 B5-L4 To be announced. B5-L5 Wnt gradient formation requires retromer function in Wnt producing cells H. Korswagen Hubrecht Laboratory, Utrecht, THE NETHERLANDS Wnt proteins function as morphogens that can form long-range concentration gradients to pattern developing tissues. We found that the retromer, a multi-protein complex involved in intracellular protein trafficking, is required for long-range signalling of the C. elegans Wnt ortholog EGL-20. The retromer functions in EGL-20/Wnt producing cells to allow the formation of an EGL-20 gradient along the an- teroposterior axis. This function is evolutionarily conserved, as Wnt target gene expression is also impaired in the absence of the retro- mer complex in vertebrates. These results demonstrate that the ability of Wnt to regulate long-range patterning events is dependent on a critical and conserved function of the retromer complex within Wnt producing cells. Putative mechanisms of retromer function in long- range Wnt signaling will be discussed. Symposia Lectures Thursday 60 C5-L1 Structural insights into mRNA degradation E. Conti 1,2 , F. Bono 1 , F. Glavan 1 and E. Lorentzen 1 1 EMBL, Heidelberg, GERMANY, 2 Max Planck Institute for Biochemistry, Martinsried, GERMANY The life span of RNAs in the cell depends on the balance between the rate with which they are synthesized and the rate with which they are degraded. Degradation is fast in the case of messenger RNAs (mRNAs) coding for gene products that need to be active only transi- ently in the cell (cell cycle regulators, transcription factors, circadian regulators etc.), as well as in the case of aberrant mRNAs that need to be rapidly destroyed before being translated into aberrant proteins. Nonsense-mediated mRNA decay (NMD) is a surveillance path- way that detects and degrades mRNA with premature stop codons (PTCs). PTCs can arise from alternative splicing, from defects in mRNA processing, and are also present in an estimated 30% of inherited genetic disorders. NMD depends on the exon junction complex (EJC) for PTC recognition and on a set of proteins (the seven SMG proteins) for targeting to mRNA degrading enzymes. SMG5, SMG6 and SMG7 share a similar domain organization, with a 14-3-3-like domain at the N-terminus that binds phosphorylated SMG2 (UPF1). The C-termini of SMG6 and SMG5 contain a PIN domain, which in the case of SMG6 functions in ribonucleolytic cleavage. The talk will focus on our current understanding of the molecular mechanisms of NMD: how the PTC-containing mRNA is recognized, how it is targeted for rapid degradation and how it is degraded. C5-L2 Structural insights into ubiquitin-like protein transfer cascades B. A. Schulman 1 , D. T. Huang 1 , H. W. Hunt 2 and M. Zhuang 3 1 HHMI/St. Jude Children’s Research Hospital, Memphis, TN, USA, 2 St. Jude Children’s Research Hospital, Memphis, TN, USA, 3 University of Tennessee/St. Jude Children’s Research Hospital, Memphis, TN, USA Post-translational modification with ubiquitin-like proteins (Ubls), such as Ubiquitin, NEDD8, SUMO and ISG15, is an essential cellu- lar regulatory mechanism. These Ubls are conjugated via serial molecular hand-offs between their own sets of E1-E2-E3 enzymes, and a target. E1s activate Ubls by catalyzing Ubl C-terminal adenylation, forming a covalent E1~Ubl thioester intermediate, and generating a thioester-linked E2~Ubl product, which must be released for subsequent reactions. We have determined the crystal structure of a trapped Ubl activation assembly-line complex containing APPBP1-UBA3 (NEDD8’s heterodimeric E1), two NEDD8s (one thioester-bound to E1’s cysteine, the other noncovalently-associated for adenylation), catalytically inactive Ubc12 (NEDD8’s E2), and MgATP. An alloster- ic, Ubl-dependent thioester switch toggles E1-E2 affinities. Two E2 binding sites depend on NEDD8 being thioester-linked to E1. One is unmasked by a striking E1 conformational change. The other comes directly from the thioester-bound NEDD8. After NEDD8 transfer to E2, reversion to an alternate E1 conformation would facilitate release of the E2~NEDD8 thioester product. Thus, successive steps in conjugation can be driven forward by each reaction inducing conformational changes and altering interaction networks to trigger the next. Thursday Symposia Lectures 61 C5-L3 Molecular machines in protein quality control and elimination of misfolded proteins D. H. Wolf University of Stuttgart, Stuttgart, GERMANY We have shown in yeast that degradation of CPY*, a soluble misfolded protein of the endoplasmic reticulum, requires an ER membrane bound machinery, the trimeric Cdc48-Ufd1-Npl4 complex as well as the UBA-UBL proteins Dsk2p and Rad23p of the cytosol for their degradation via the ubiquitin-proteasome system (Kostova and Wolf EMBO J. 2003; 22: 2309–2317; Medicherla et al. EMBO Rep. 2004; 5: 602–697). We furthermore showed that ER import defective CPY* (DssCPY*), derivatives thereof (e.g. DssCPY*-GPF), or even ER import incompetent wild type CPY (DssCPY) are rapidly degraded via the cytosolic ubiquitin proteasome system (Park et al. Mol. Bio. Cell 2007; 18: 153–165). In contrast to the soluble ERAD substrate CPY*, degradation of these proteins is independent of the tri- meric Cdc48-Ufd1-Npl4 complex as well as of Dsk2p and Rad23p. Instead, their degradation requires the cytosolic Hsp70 chaperones of the Ssa type as well as the co-chaperone Ydj1p. The Hsp90 machinery is not involved in the degradation process. We show that the Hsp70 Ssa1 is able to re-solubilize precipitated DssCPY*-GFP material, keeps it soluble and targets it to the proteasome. C5-L4 Regulation of proteasome activity by Hul5 and Ubp6 D. Finley 1 , J. Hanna 1 , B. Crosas 2 , N. Hathaway 1 , Y. Tone 1 , P. Zhang 1 , S. Elsasser 1 , D. Kirkpatrick 1 , S. P. Gygi 1 and R. W. King 1 1 Harvard Medical School, Boston, MA, USA, 2 Institut de Biologia Molecular, Barcelona, SPAIN Ubp6 is a proteasome-associated deubiquitinating enzyme. We have found that Ubp6 can inhibit the proteasome. Surprisingly, inhibition does not require Ubp6 catalytic activity. Deubiquitination and proteasome inhibition by Ubp6 cooperate in that inhibition of degradation by Ubp6 is accompanied by progressive trimming of substrate-bound ubiquitin groups. Thus, Ubp6 regulates both the nature and magni- tude of proteasome activity. Proteasome deficiency stimulates a stress response in which proteasomes are induced. We have found a new regulatory pathway, the ubiquitin stress response, in which Ubp6, which spares ubiquitin from proteasomal degradation, is induced. Enhanced loading of proteasomes with Ubp6 alters proteasome function. However, in contrast with proteasome stress, ubiquitin stress does not elevate proteasome levels. Thus, homeostatic control of the ubiquitin-proteasome pathway can be achieved through signal- dependent, subunit-specific regulation of the proteasome. We have also found that the ubiquitin ligase Hul5 serves to extend the chains of proteasome-bound ubiquitin conjugates. Accordingly, hul5 mutants show reduced degradation rates for many substrates. Hul5 binding to proteasomes is stabilized by Ubp6, and the products of Hul5 conjugation can be rapidly disassembled by proteasome-bound Ubp6. By regulating the lengths of proteasome-bound ubiquitin chains, the balance of Hul5 and Ubp6 activity might regulate substrate commitment to degradation. Symposia Lectures Thursday 62 C5-L5 Mechanism, function and regulation of SUMOylation F. Melchior University of Goettingen, Goettingen, GERMANY Small ubiquitin related modifier SUMO-1 and its homologs can be reversibly conjugated to a large number of cellular proteins. Depend- ing on the target, SUMOylation may regulate protein interactions, alter intracellular localization, influence stability, or alter activity. Examples from our work are (i) the finding that SUMOylation is required for RanGAP1 association with the nuclear pore complex pro- tein RanBP2/Nup358; (ii) the finding that SUMOylation of the ubiquitin conjugating enzyme E2–25k interferes with E1 interaction. SUMOylation involves an enzymatic cascade that resembles ubiquitination, and can be reverted by isopeptidases. The E1 activating enzyme Aos1/Uba2 and the E2 conjugating enzyme Ubc9 are sufficient for modification of some targets, others require E3 ligases such as PIAS proteins or RanBP2. While SUMOylation has emerged as an important regulatory mechanism of protein function, little is known about regulation of sumoylation itself. While various stresses such as heat shock are known to increase sumoylation, we found that the reactive oxygen species H 2 O 2 , supplied exogenously or produced endogenously, leads to direct and reversible inhibition of SUMO conjugating enzymes. These findings add SUMO enzymes to the small list of direct effectors of H2O2 and implicate ROS as key regulators of the sumoylation-desumoylation equilibrium. References 1. Mahajan R, Delphin C, Guan T, Gerace L, Melchior F. Cell 1997; 88: 97–107. 2. Pichler A, Gast A, Seeler JS, Dejean A, Melchior F. Cell 2002; 108: 109–120. 3. Pichler A, Knipscheer P, Oberhofer E, van Dijk WJ, Koerner R, Olsen JV, Jentsch S, Melchior F, Sixma TK. Nat. Struct. & Mol. Biol. 2005; 12: 264–269. 4. Bossis G, Melchior F. Mol Cell 2006; 21: 349–357. D5-L1 Molecular traffic through metabolic networks U. Sauer ETH Zurich, Zurich, SWITZERLAND The direction and rate of molecular fluxes through metabolic networks depend on thermodynamics, kinetic properties of the participa- ting enzyme(s), and a complicated regulatory network that includes transcriptional and allosteric regulation. Hence, intracellular fluxes are the functional output of integrated biochemical and genetic interactions within complex metabolic networks that are pivotal for understanding of network operation (1). In contrast to the directly measurable concentrations of metabolites and proteins, however, fluxes are per se non measurable and must be inferred from other quantities. For this reason, quantification of intracellular fluxes has long lagged behind our capability to track global metabolite, mRNA or protein concentration changes. With recent advances in 13C- labeling experiments, large-scale experimental analysis of intracellular fluxes is now feasible (2). After a brief introduction of the princi- ples of flux analysis, design principles of carbon traffic that include network rigidity and robustness as well as the relevance of genetic regulation will be discussed for B. subtilis and E. coli. Finally, we will address the question whether or not flux responses to gene dele- tions or environmental conditions can be predicted computationally with stoichiometric network models and flux balance analysis. Reference 1. Sauer U. Mol. Sys. Biol. 2006; 2: 62–68.2. Fischer E, Sauer U. Nat. Genet. 2005; 37: 636–640. Thursday Symposia Lectures 63 D5-L2 TOR signalling and control of cell growth in yeast and mammals M. N. Hall Biozentrum, University of Basel, Basel, SWITZERLAND TOR (target of rapamycin) is a highly conserved serine/threonine kinase that controls cell growth and metabolism in response to nutrients, growth factors, cellular energy, and stress. TOR was originally discovered in yeast, but has since been shown to be conserved in all eukaryo- tes including plants, worms, flies, and mammals. The discovery of TOR led to a fundamental change in how one thinks of cell growth. It is not a spontaneous process that simply happens when building blocks (nutrients) are available, but rather is a highly regulated, plastic pro- cess that is controlled by TOR-dependent signalling pathways. TOR is found in two structurally and functionally distinct multiprotein com- plexes, TORC1 and TORC2. The two TOR complexes, like TOR itself, are highly conserved. Yeast TORC1 is rapamycin sensitive, and contains KOG1, LST8 and either TOR1 or TOR2. The mammalian counterpart of TORC1, mTORC1, contains raptor (mKOG1), mLST8, and mTOR. TORC1 in yeast and mammals mediates temporal control of cell growth by regulating several cellular processes including trans- lation, transcription, ribosome biogenesis, nutrient transport and autophagy. Yeast TORC2 is rapamycin insensitive, and contains AVO1, AVO2, AVO3, BIT61, LST8, and TOR2. mTORC2 is also rapamycin insensitive and contains SIN1 (mAVO1), rictor (mAVO3), mLST8, and mTOR. TORC2 in yeast and mammals mediates spatial control of cell growth by regulating the actin cytoskeleton. Thus, the two TOR complexes constitute an ancestral signalling network conserved throughout eukaryotic evolution to control the fundamental process of cell growth. The physiological consequences of mTORC1 dysregulation suggest that inhibitors of mTOR may be useful in the treatment of can- cer, cardiovascular disease, autoimmunity, and metabolic disorders. D5-L3 Small molecules, genes and complex traits L. Willmitzer Max Planck Institut fu ¨ r Molekulare Pflanzenphysiologie, Potsdam, GERMANY Small molecules are the third level of realization of genetic information. In recent years techniques (mostly mass spectroscopy base) have been developed which allow the monitoring of at least a certain fraction of small molecules/metabolites in a reliable and high through put fashion. The application of metabolomics in three different areas will be discussed:- Gene annotation/fast breeding Prediction of complex traits such as biomass Identification of candidate signalling molecules. Symposia Lectures Thursday 64 D5-L4 Novel regulatory mechanism for glycogen synthesis J. J. Guinovart 1,2 1 Institute for Research in Biomedicine, Barcelona, SPAIN, 2 University of Barcelona, Barcelona, SPAIN A novel regulatory mechanism for glycogen synthesis that controls the levels of the key enzyme Glycogen Syntase will be described. This regulatory mechanism involves the ubiquitin-proteasome pathway and requires the interaction between laforin and malin. Disturbance of this mechanism, as a consequence of mutations in laforin or malin, will lead to the accumulation of glycogen-like intracellular inclusions and the development of Lafora Disease (progressive myoclonus epilepsy). These findings unveil a previously unknown mechanism of blockage of glycogen synthesis, which would act in addition to the well characterized control by phosphorylation and allosteric regulation of glycogen synthase. D5-L5 Evolution of metabolic networks in microbes C. Pal 1,2 1 Eotvos Lorand University, Budapest, HUNGARY, 2 University of Oxford, Oxford, UK Numerous studies have considered the early evolution of metabolic pathways, but the modes of recent evolution of metabolic networks are poorly understood. Our work integrates comparative genomics, systems biology and microbial selection experiments to examine (i) the contribution of different genetic mechanisms to network growth; (ii) the selective forces driving reductive and adaptive network evo- lution of and (iii) integration of new nodes to the network. In sharp contrast to eukaryotes, most changes in bacterial networks are due to horizontal gene transfer, with little contribution from gene duplicates. Networks generally grow by acquiring genes involved in the transport and catalysis of external nutrients, whereas central parts of the network remain evolutionarily stable. As a by-product of adap- tation to changing environmental conditions, these networks are also becoming more resilient to the impact of harmful mutations. Thus, our work supports the view that functional redundancy may be more apparent than real, and it offers a unified framework for the evolu- tion of environmental adaptation and mutational robustness. Remarkably, newly developed systems biology tools also shed new lights on evolutionary outcome of genome minimalization in endosymbiotic bacteria. Thursday Symposia Lectures 65 [...].. .Symposia Lectures Thursday E5-L1 Probing ribosome functions by nucleotide analog interference N Polacek1, M Amort1, M Erlacher1 and R Micura2 1 Innsbruck Biocenter, Innsbruck, AUSTRIA, 2Leopold-Franzens-University,... to secondary binding sites of the receptor Currently available structural/functional data from the receptor Pex5p and other complexes from the peroxisomal translocon will be presented 66 Thursday Symposia Lectures E5-L3 Control of microtubule-kinetochore attachment in mitosis A Musacchio European Institute of Oncology, Milan, ITALY Our laboratory is interested in the mechanisms responsible for the... experiment CAPRI (critical assessment of PRedicted interactions) New developments in multi-body docking will be presented which should open the route to the modelling of larger molecular machines 67 Symposia Lectures Thursday E5-L5 Insight into alternative-splicing mechanisms with the solution structures of several RRM-RNA complexes F Allain ETH Zu ¨rich, Zu ¨rich, SWITZERLAND No abstract available 68 . Mole- cule) gene exon whose inclusion is modulated during long term potentiation. Symposia Lectures Thursday 56 A5-L3 snRNP and spliceosome assembly in vivo K. Neugebauer Max. Biophysical Chemistry, Go ¨ ttingen, GERMANY No abstract available. Thursday Symposia Lectures 57 A5-L5 mRNA quality control: an ancient machinery recognizes