Molecular Biology Institute of Barcelona IBMB CSIC

Montcada i Reixac, Spain

Molecular Biology Institute of Barcelona IBMB CSIC

Montcada i Reixac, Spain
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Cota R.R.,Barcelona Institute for Research in Biomedicine | Teixido-Travesa N.,Barcelona Institute for Research in Biomedicine | Ezquerra A.,Barcelona Institute for Research in Biomedicine | Eibes S.,Barcelona Institute for Research in Biomedicine | And 4 more authors.
Journal of Cell Science | Year: 2017

Regulation of the γ-tubulin ring complex (γTuRC) through targeting and activation restricts nucleation of microtubules to microtubuleorganizing centers (MTOCs), aiding in the assembly of ordered microtubule arrays. However, the mechanistic basis of this important regulation remains poorly understood. Here, we show that, in human cells, γTuRC integrity, determined by the presence of γ-tubulin complex proteins (GCPs; also known as TUBGCPs) 2-6, is a prerequisite for interaction with the targeting factor NEDD1, impacting on essentially all γ-tubulin-dependent functions. Recognition of γTuRC integrity is mediated by MZT1, which binds not only to the GCP3 subunit as previously shown, but cooperatively also to other GCPsthrough a conserved hydrophobic motif present in the N-termini of GCP2, GCP3, GCP5 and GCP6. MZT1 knockdown causes severe cellular defects under conditions that leave γTuRC intact, suggesting that the essential function of MZT1 is not in γTuRC assembly. Instead, MZT1 specifically binds fully assembled γTuRC to enable interaction with NEDD1 for targeting, and with the CM1 domain of CDK5RAP2 for stimulating nucleation activity. Thus, MZT1 is a 'priming factor' for γTuRC that allows spatial regulation of nucleation. © 2017. Published by The Company of Biologists Ltd.

Ortiz R.,Molecular Biology Institute of Barcelona IBMB CSIC | Georgieva M.V.,Molecular Biology Institute of Barcelona IBMB CSIC | Gutierrez S.,Molecular Biology Institute of Barcelona IBMB CSIC | Pedraza N.,University of Lleida | And 2 more authors.
Cell Reports | Year: 2017

Regulation of mRNA localization is a conserved cellular process observed in many types of cells and organisms. Asymmetrical mRNA distribution plays a particularly important role in the nervous system, where local translation of localized mRNA represents a key mechanism in synaptic plasticity. CaMKIIα is a very abundant mRNA detected in neurites, consistent with its crucial role at glutamatergic synapses. Here, we report the presence of CaMKIIα mRNA isoforms that contain intron i16 in dendrites, RNA granules, and synaptoneurosomes from primary neurons and brain. This subpopulation of unspliced mRNA preferentially localizes to distal dendrites in a synaptic-activity-dependent manner. Staufen2, a well-established marker of RNA transport in dendrites, interacts with intron i16 sequences and enhances its distal dendritic localization, pointing to the existence of intron-mediated mechanisms in the molecular pathways that modulate dendritic transport and localization of synaptic mRNAs. © 2017 The Author(s)

Meyer M.,Molecular Biology Institute of Barcelona IBMB CSIC | Macias S.,Western General Hospital MRC | Labrador M.,Molecular Biology Institute of Barcelona IBMB CSIC | Vilardell J.,Catalan Institution for Research and Advanced Studies
RNA | Year: 2010

Pre-mRNA splicing is catalyzed by the spliceosome, and its control is essential for correct gene expression. While splicing repressors typically interfere with transcript recognition by spliceosomal components, the yeast protein L30 blocks spliceosomal rearrangements required for the engagement of U2 snRNP (small ribonucleoprotein particle) to its own transcript RPL30. Using a mutation in the RPL30 binding site that disrupts this repression, we have taken a genetic approach to reveal that regulation of splicing is restored in this mutant by deletion of the cap-binding complex (CBC) component Cbp80. Indeed, our data indicate that Cbp80 plays distinct roles in the recognition of the intron by U1 and U2 snRNP. It promotes the initial 5′ splice site recognition by U1 and, independently, facilitates U2 recruitment, depending on sequences located in the vicinity of the 5′ splice site. These results reveal a novel function for CBC in splicing and imply that these molecular events can be the target of a splicing regulator.

Garcia-Prat L.,University Pompeu Fabra | Martinez-Vicente M.,CIBER ISCIII | Perdiguero E.,University Pompeu Fabra | Ortet L.,University Pompeu Fabra | And 10 more authors.
Nature | Year: 2016

During ageing, muscle stem-cell regenerative function declines. At advanced geriatric age, this decline is maximal owing to transition from a normal quiescence into an irreversible senescence state. How satellite cells maintain quiescence and avoid senescence until advanced age remains unknown. Here we report that basal autophagy is essential to maintain the stem-cell quiescent state in mice. Failure of autophagy in physiologically aged satellite cells or genetic impairment of autophagy in young cells causes entry into senescence by loss of proteostasis, increased mitochondrial dysfunction and oxidative stress, resulting in a decline in the function and number of satellite cells. Re-establishment of autophagy reverses senescence and restores regenerative functions in geriatric satellite cells. As autophagy also declines in human geriatric satellite cells, our findings reveal autophagy to be a decisive stem-cell-fate regulator, with implications for fostering muscle regeneration in sarcopenia. © 2016 Macmillan Publishers Limited. All rights reserved.

Benabou S.,University of Barcelona | Ferreira R.,CSIC - Institute of Advanced Chemistry of Catalonia | Avino A.,CSIC - Institute of Advanced Chemistry of Catalonia | Gonzalez C.,CSIC - Institute of Physical Chemistry "Rocasolano" | And 5 more authors.
Biochimica et Biophysica Acta - General Subjects | Year: 2014

Background Cytosine- and guanine-rich regions of DNA are capable of forming complex structures named i-motifs and G-quadruplexes, respectively. In the present study the solution equilibria at nearly physiological conditions of a 34-base long cytosine-rich sequence and its complementary guanine-rich strand corresponding to the first intron of the n-myc gene were studied. Both sequences, not yet studied, contain a 12-base tract capable of forming stable hairpins inside the i-motif and G-quadruplex structures, respectively. Methods Spectroscopic, mass spectrometry and separation techniques, as well as multivariate data analysis methods, were used to unravel the species and conformations present. Results The cytosine-rich sequence forms two i-motifs that differ in the protonation of bases located in the loops. A stable Watson-Crick hairpin is formed by the bases in the first loop, stabilizing the i-motif structure. The guanine-rich sequence adopts a parallel G-quadruplex structure that is stable throughout the pH range 3-7, despite the protonation of cytosine and adenine bases at lower pH values. The presence of G-quadruplex aggregates was confirmed using separation techniques. When mixed, G-quadruplex and i-motif coexist with the Watson-Crick duplex across a pH range from approximately 3.0 to 6.5. Conclusions Two cytosine- and guanine-rich sequences in n-myc gene may form stable i-motif and G-quadruplex structures even in the presence of long loops. pH modulates the equilibria involving the intramolecular structures and the intermolecular Watson-Crick duplex. General significance Watson-Crick hairpins located in the intramolecular G-quadruplexes and i-motifs in the promoter regions of oncogenes could play a role in stabilizing these structures. © 2013 Elsevier B.V.

Pedraza N.,Molecular Biology Institute of Barcelona IBMB CSIC | Ortiz R.,Molecular Biology Institute of Barcelona IBMB CSIC | Cornado A.,Molecular Biology Institute of Barcelona IBMB CSIC | Llobet A.,University of Barcelona | And 2 more authors.
Journal of Neuroscience | Year: 2014

Local regulation of protein synthesis allows a neuron to rapidly alter the proteome in response to synaptic signals, an essential mechanism in synaptic plasticity that is altered in many neurological diseases. Synthesis of many synaptic proteins is under local control and much of this regulation occurs through structures termed RNA granules. KIS is a protein kinase that associates with stathmin, a modulator of the tubulin cytoskeleton. Furthermore, KIS is found in RNA granules and stimulates translation driven by the β-actin 3 'UTR in neurites. Here we explore the physiological and molecular mechanisms underlying the action of KIS on hippocampal synaptic plasticity in mice. KIS downregulation compromises spine development, alters actin dynamics, and reduces postsynaptic responsiveness. The absence of KIS results in a significant decrease of protein levels of PSD-95, a postsynaptic scaffolding protein, and the AMPAR subunits GluR1 and GluR2 in a CPEB3-dependent manner. Underlying its role in spine maturation, KIS is able to suppress the spine developmental defects caused by CPEB3 overexpression. Moreover, either by direct or indirect mechanisms, KIS counteracts the inhibitory activity of CPEB3 on the GluR2 3 'UTR at both mRNA translation and polyadenylation levels. Our study provides insights into the mechanisms that mediate dendritic spine morphogenesis and functional synaptic maturation, and suggests KIS as a link regulating spine cytoskeleton and postsynaptic activity in memory formation. © 2014 the authors.

Repiso A.,University of Barcelona | Repiso A.,Molecular Biology Institute of Barcelona IBMB CSIC | Bergantinos C.,University of Barcelona | Bergantinos C.,Columbia University | Serras F.,University of Barcelona
Development (Cambridge) | Year: 2013

To understand the cellular parameters that govern Drosophila wing disc regeneration, we genetically eliminated specific stripes of the wing disc along the proximodistal axis and used vein and intervein markers to trace tissue regeneration. We found that veins could regenerate interveins and vice versa, indicating respecification of cell fates. Moreover, respecification occurred in cells close to the wound. The newly generated domains were intercalated to fill in the missing parts. This intercalation was driven by increased proliferation, accompanied by changes in the orientation of the cell divisions. This reorientation depended on Fat (Ft) and Crumbs (Crb), which acted, at least partly, to control the activity of the effector of the Hippo pathway, Yorkie (Yki). Increased Yki, which promotes proliferation, affected the final shape and size. Heterozygous ft or crb, which normally elicit size and shape defects in regenerated wings, could be rescued by yki heterozygosity. Thus, Ft and Crb act as sensors to drive cell orientation during intercalary regeneration and control Yki levels to ensure a proper balance between proliferation and cell reorientation. We propose a model based on intercalation of missing cell identities, in which a coordinated balance between orientation and proliferation is required for normal organ shape and size. © 2013. Published by The Company of Biologists Ltd.

Querol-Audi J.,University of California at Berkeley | Querol-Audi J.,Molecular Biology Institute of Barcelona IBMB CSIC | Sun C.,University of California at Berkeley | Vogan J.M.,University of California at Berkeley | And 6 more authors.
Structure | Year: 2013

Eukaryotic translation initiation factor 3 (eIF3) plays a central role in protein synthesis by organizing the formation of the 43S preinitiation complex. Using genetic tag visualization by electron microscopy, we reveal the molecular organization of ten human eIF3 subunits, including an octameric core. The structure of eIF3 bears a close resemblance to that of the proteasome lid, with a conserved spatial organization of eight core subunits containing PCI and MPN domains that coordinate functional interactions in both complexes. We further show that eIF3 subunits a and c interact with initiation factors eIF1 and eIF1A, which control the stringency of start codon selection. Finally, we find that subunit j, which modulates messenger RNA interactions with the small ribosomal subunit, makes multiple independent interactions with the eIF3 octameric core. These results highlight the conserved architecture of eIF3 and how it scaffolds key factors that control translation initiation in higher eukaryotes, including humans. © 2013 Elsevier Ltd. All rights reserved.

Smith M.D.,University of California at Berkeley | Gu Y.,University of California at Berkeley | Querol-Audi J.,University of California at Berkeley | Querol-Audi J.,Molecular Biology Institute of Barcelona IBMB CSIC | And 4 more authors.
PLoS ONE | Year: 2013

Eukaryotic translation initiation factor 3 (eIF3) is a key regulator of translation initiation, but its in vivo assembly and molecular functions remain unclear. Here we show that eIF3 from Neurospora crassa is structurally and compositionally similar to human eIF3. N. crassa eIF3 forms a stable 12-subunit complex linked genetically and biochemically to the 13th subunit, eIF3j, which in humans modulates mRNA start codon selection. Based on N. crassa genetic analysis, most subunits in eIF3 are essential. Subunits that can be deleted (e, h, k and l) map to the right side of the eIF3 complex, suggesting that they may coordinately regulate eIF3 function. Consistent with this model, subunits eIF3k and eIF3l are incorporated into the eIF3 complex as a pair, and their insertion depends on the presence of subunit eIF3h, a key regulator of vertebrate development. Comparisons to other eIF3 complexes suggest that eIF3 assembles around an eIF3a and eIF3c dimer, which may explain the coordinated regulation of human eIF3 levels. Taken together, these results show that Neurospora crassa eIF3 provides a tractable system for probing the structure and function of human-like eIF3 in the context of living cells. © 2013 Smith et al.

Yahya G.,Molecular Biology Institute of Barcelona IBMB CSIC | Parisi E.,Molecular Biology Institute of Barcelona IBMB CSIC | Flores A.,Molecular Biology Institute of Barcelona IBMB CSIC | Gallego C.,Molecular Biology Institute of Barcelona IBMB CSIC | Aldea M.,Molecular Biology Institute of Barcelona IBMB CSIC
Molecular Cell | Year: 2014

Cells commit to a new cell cycle at Start by activation of the G1 Cdk-cyclin complex which, in turn, triggers a genome-wide transcriptional wave that executes the G1/S transition. In budding yeast, the Cdc28-Cln3 complex is regulated by an ER-retention mechanism that is important for proper cell size control. We have isolated small-cell-size CDC28 mutants showing impaired retention at the ER and premature accumulation of the Cln3 cyclin in the nucleus. The differential interactome of a quintuple Cdc28wee mutant pinpointed Whi7, a Whi5 paralog targeted by Cdc28 that associates to the ER in a phosphorylation-dependent manner. Our results demonstrate that the Cln3 cyclin and Whi7 act in a positive feedback loop to release the G1 Cdk-cyclin complex and trigger Start once a critical size has been reached, thus uncovering a key nonlinear mechanism at the earliest known events of cell-cycle entry. © 2014 Elsevier Inc.

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