A role for the Cajal-body-associated SUMO isopeptidase USPL1 in snRNA transcription mediated by RNA polymerase II

Cajal bodies are nuclear structures that are involved in biogenesis of snRNPs and snoRNPs, maintenance of telomeres and processing of histone mRNA. Recently, the SUMO isopeptidase USPL1 was identified as a component of Cajal bodies that is essential for cellular growth and Cajal body integrity. However, a cellular function for USPL1 is so far unknown. Here, we use RNAi-mediated knockdown in human cells in combination with biochemical and fluorescence microscopy approaches to investigate the function of USPL1 and its link to Cajal bodies. We demonstrate that levels of snRNAs transcribed by RNA polymerase (RNAP) II are reduced upon knockdown of USPL1 and that downstream processes such as snRNP assembly and pre-mRNA splicing are compromised. Importantly, we find that USPL1 associates directly with U snRNA loci and that it interacts and colocalises with components of the Little Elongation Complex, which is involved in RNAPII-mediated snRNA transcription. Thus, our data indicate that USPL1 plays a key role in RNAPII-mediated snRNA transcription

Neurochondrin interacts with the SMN protein suggesting a novel mechanism for Spinal Muscular Atrophy pathology

Work in the Sleeman laboratory by Luke Thompson was funded by MRC-CASE studentship MR/K016997/1. This work was also supported by the Wellcome Trust [grant number 094476/Z/10/Z], which funded the purchase of the TripleTOF 5600 mass spectrometer at the BSRC Mass Spectrometry and Proteomics Facility, University of St Andrews.Spinal Muscular Atrophy (SMA) is an inherited neurodegenerative condition caused by reduction in functional Survival Motor Neurones Protein (SMN). SMN has been implicated in transport of mRNA in neural cells for local translation. We previously identified microtubule-dependant mobile vesicles rich in SMN and the splicing factor SmB, a member of the Sm protein family, in neural cells. By comparing the proteome of SmB to that of SmN, a neural-specific Sm protein, we now show that the essential neural protein neurochondrin (NCDN) interacts with Sm proteins and SMN in the context of mobile vesicles in neurites. NCDN has roles in protein localisation in neural cells, and in maintenance of cell polarity. NCDN is required for the correct localisation of SMN, suggesting they may both be required for formation and transport of trafficking vesicles. NCDN provides a potential therapeutic target for SMA together with, or in place of, those targeting SMN expression.Publisher PDFPeer reviewe

The significant other: splicing by the minor spliceosome

Peer reviewe

Study of the molecular basis of the spinal muscular atrophy SMA

L'Atrophie Musculaire spinale (SMA) est une maladie neurodégénérative causée par des mutations du gène SMN1 et caractérisée par la dégénérescence sélective des motoneurones alpha de la moelle épinière. les mécanismes moléculaires de la SMA ne sont aps clairs. cependant, deux hypothèses ont été retenues:D'une part, que la déficience en SMN entraine une perturbation de la biogenèse des snRNPs spliceosomales individuelles et par conséquent des défauts d'épissage. pendant ma thèse, nous avons montré que la déficience en SMN provoquait une diminution des particules tri-snRNPs majeures amis surtout mineures et que cela avait des conséquences sur l'épissage d'un sous-groupe de pré-ARNm contenant des introns mineurs.D'autre part, que la déficience en SMN entraine des altérations de transport d'ARN dans les axones, essentiels pour la survie des motoneurones. A part l'ARNm de la beta-actine et l'ARNm de cpg15 récemment identifié, ceux qui pourraient être transportés par SMN n'ont pas été décrits. nous avons donc identifié les ARN interagissant avec les isoformes a-SMN et SMN-fl dans des cellules neuronales, et montré que certains de ces ARN cibles colocalisent avec SMN dans les axones, suggérant qu'elle est impliquée dans leur transport.Spinal Muscular Atrophy is a neurodegenerative disease caused by mutations in SMN1 gene. SMA is characterized by the loss of alpha-motoneurons of the spinal cord. However, the precise molecular mechanisms underlying the disease are still unkown. two hypotheses have been retained to explain SMA pathigenesis:In one hand, the fact that SMN deficiency leads to a perturbation of individual snRNPs biogenesis and consequently splicing defects. During my PhD, we have shown that SMN deficiency alters the levels of major, but mostly, minor tri-snRNPs. And that leads to splicing defects of a subset of pre-mRNA containing minor introns.In the other hand, that SMN deficiency causes alteration of axonal transport of RNAs crucial to motoneurons survival. Except beta-actin mRNA and the recently identified cpg mRNA, the RNA targets of SMN have not been described. We succeed to identify RNA targets of both a-SMN and SMN-fl isoformes in a neuronal cell line and colocalisation data of some of these targets suggested that SMN could be implicated in the transport of these RNAs

Etude des bases moléculaires de l'atrophie musculaire spinale

L'Atrophie Musculaire spinale (SMA) est une maladie neurodégénérative causée par des mutations du gène SMN1 et caractérisée par la dégénérescence sélective des motoneurones alpha de la moelle épinière. les mécanismes moléculaires de la SMA ne sont aps clairs. cependant, deux hypothèses ont été retenues:D'une part, que la déficience en SMN entraine une perturbation de la biogenèse des snRNPs spliceosomales individuelles et par conséquent des défauts d'épissage. pendant ma thèse, nous avons montré que la déficience en SMN provoquait une diminution des particules tri-snRNPs majeures amis surtout mineures et que cela avait des conséquences sur l'épissage d'un sous-groupe de pré-ARNm contenant des introns mineurs.D'autre part, que la déficience en SMN entraine des altérations de transport d'ARN dans les axones, essentiels pour la survie des motoneurones. A part l'ARNm de la beta-actine et l'ARNm de cpg15 récemment identifié, ceux qui pourraient être transportés par SMN n'ont pas été décrits. nous avons donc identifié les ARN interagissant avec les isoformes a-SMN et SMN-fl dans des cellules neuronales, et montré que certains de ces ARN cibles colocalisent avec SMN dans les axones, suggérant qu'elle est impliquée dans leur transport.Spinal Muscular Atrophy is a neurodegenerative disease caused by mutations in SMN1 gene. SMA is characterized by the loss of alpha-motoneurons of the spinal cord. However, the precise molecular mechanisms underlying the disease are still unkown. two hypotheses have been retained to explain SMA pathigenesis:In one hand, the fact that SMN deficiency leads to a perturbation of individual snRNPs biogenesis and consequently splicing defects. During my PhD, we have shown that SMN deficiency alters the levels of major, but mostly, minor tri-snRNPs. And that leads to splicing defects of a subset of pre-mRNA containing minor introns.In the other hand, that SMN deficiency causes alteration of axonal transport of RNAs crucial to motoneurons survival. Except beta-actin mRNA and the recently identified cpg mRNA, the RNA targets of SMN have not been described. We succeed to identify RNA targets of both a-SMN and SMN-fl isoformes in a neuronal cell line and colocalisation data of some of these targets suggested that SMN could be implicated in the transport of these RNAs.MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Impaired minor tri-snRNP assembly generates differential splicing defects of U12-type introns in lymphoblasts derived from a type I SMA patient

International audienc

Impaired minor tri-snRNP assembly generates differential splicing defects of U12-type introns in lymphoblasts derived from a type I SMA patient

The survival of motor neuron (SMN) protein is essential for cytoplasmic assembly of spliceosomal snRNPs. Although the normal proportion of endogenous snRNAs is unevenly altered in spinal muscular atrophy (SMA) tissues, the biogenesis of individual snRNPs is not dramatically affected in SMN-deficient cells. The SMN protein is also required for normal Cajal body (CB) formation, but the functional consequences of CB disruption upon SMN deficiency have not yet been analyzed at the level of macromolecular snRNPs assembly. Here, we show that the SMN protein is required for tri-snRNPs formation and that the level of the minor U4atac/U6atac/U5 tri-snRNPs is dramatically decreased in lymphoblasts derived from a patient suffering from a severe form of SMA. We found also that splicing of some, but not all, minor introns is inhibited in these cells, demonstrating links between SMN deficiency and differential alterations of splicing events mediated by the minor spliceosome. Our results suggest that SMA might result from the inefficient splicing of one or only a few pre-mRNAs carrying minor introns and coding for proteins required for motor neurons function and/or organization

Genome-wide identification of mRNAs associated with the protein SMN whose depletion decreases their axonal localization

Spinal muscular atrophy is a neuromuscular disease resulting from mutations in the SMN1 gene, which encodes the survival motor neuron (SMN) protein. SMN is part of a large complex that is essential for the biogenesis of spliceosomal small nuclear RNPs. SMN also colocalizes with mRNAs in granules that are actively transported in neuronal processes, supporting the hypothesis that SMN is involved in axonal trafficking of mRNPs. Here, we have performed a genome-wide analysis of RNAs present in complexes containing the SMN protein and identified more than 200 mRNAs associated with SMN in differentiated NSC-34 motor neuron-like cells. Remarkably, approximately 30% are described to localize in axons of different neuron types. In situ hybridization and immuno-fluorescence experiments performed on several candidates indicate that these mRNAs colocalize with the SMN protein in neurites and axons of differentiated NSC-34 cells. Moreover, they localize in cell processes in an SMN-dependent manner. Thus, low SMN levels might result in localization deficiencies of mRNAs required for axonogenesis

COPA syndrome as a cause of lupus nephritis

International audienceGenetic kidney diseases are rare situations resulting from mutations in genes expressed in major structures of the kidney, including podocytes, tubular cells, and basement membrane.1 More recently, a new field of monogenic inflammatory diseases has been identified2; these immune-mediated diseases can affect all organs, including the kidney. Here we report on a young girl diagnosed with lupus nephritis and carrying a mutation in the COPA gene encoding for coatomer protein complex subunit alpha