Publications (26)165.63 Total impact
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Article: Identity and ranking of colonic mesenchymal stromal cells.
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ABSTRACT: Although ongoing clinical trials utilize systemic administration of bone-marrow mesenchymal stromal cells (BM-MSCs) in Crohn's disease (CD), nothing is known about the presence and the function of mesenchymal stromal cells (MSCs) in the normal human bowel. MSCs are bone marrow (BM) multipotent cells supporting hematopoiesis with the potential to differentiate into multiple skeletal phenotypes. A recently identified new marker, CD146, allowing to prospectively isolate MSCs from BM, renders also possible their identification in different tissues. In order to elucidate the presence and functional role of MSCs in human bowel we analyzed normal adult colon sections and isolated MSCs from them. In colon (C) sections, resident MSCs form a net enveloping crypts in lamina propria, coinciding with structural myofibroblasts or interstitial stromal cells. Nine sub-clonal CD146(+) MSC lines were derived and characterized from colon biopsies, in addition to MSC lines from five other human tissues. In spite of a phenotype qualitative identity between the BM- and C-MSC populations, they were discriminated and categorized. Similarities between C-MSC and BM-MSCs are represented by: Osteogenic differentiation, hematopoietic supporting activity, immune-modulation, and surface-antigen qualitative expression. The differences between these populations are: C-MSCs mean intensity expression is lower for CD13, CD29, and CD49c surface-antigens, proliferative rate faster, life-span shorter, chondrogenic differentiation rare, and adipogenic differentiation completely blocked. Briefly, BM-MSCs, deserve the rank of progenitors, whereas C-MSCs belong to the restricted precursor hierarchy. The presence and functional role of MSCs in human colon provide a rationale for BM-MSC replacement therapy in CD, where resident bowel MSCs might be exhausted or diverted from their physiological functions.Journal of Cellular Physiology 12/2011; 227(9):3291-300. · 3.87 Impact Factor -
Article: Critical Role of c-Myc in Acute Myeloid Leukemia Involving Direct Regulation of miR-26a and Histone Methyltransferase EZH2.
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ABSTRACT: Increased expression or aberrant activation of c-Myc plays an important role in leukemogenesis. Here, we show that in acute myeloid leukemia (AML), c-Myc directly controls the expression of EZH2, a component of the Polycomb repressive complex 2, and miR-26a. miR-26a is downregulated in primary blasts from AML patients and, during myeloid differentiation of AML cells, is induced together with a decrease in c-Myc and Ezh2 levels. Previously, EZH2 was shown to be regulated by miR-26a at the translational levels in lymphomas. However, we demonstrate that in AML, the variation of EZH2 mainly depends on c-Myc transcriptional control. We also show that enforced expression of miR-26a in AML cells is able to inhibit cell cycle progression by downregulating cyclin E2 expression. In addition, increased levels of miR-26a potentiate the antiproliferative effects of 1,25-dihydroxyvitamin D(3) (VitD) and stimulate myeloid differentiation. Our results identify new molecular targets of c-Myc in AML and highlight miR-26a attractiveness as a therapeutic target in leukemia.Genes & cancer 05/2011; 2(5):585-92. -
Article: Gene expression profiling identifies a subset of adult T-cell acute lymphoblastic leukemia with myeloid-like gene features and over-expression of miR-223.
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ABSTRACT: Until recently, few molecular aberrations were recognized in acute lymphoblastic leukemia of T-cell origin; novel lesions have recently been identified and a certain degree of overlap between acute myeloid leukemia and T-cell acute lymphoblastic leukemia has been suggested. To identify novel T-cell acute lymphoblastic leukemia entities, gene expression profiling was performed and clinico-biological features were studied. Sixty-nine untreated adults with T-cell acute lymphoblastic leukemia were evaluated by oligonucleotide arrays: unsupervised and supervised analyses were performed. The up-regulation of myeloid genes and miR-223 expression were validated by quantitative polymerase chain reaction analysis. Using unsupervised clustering, we identified five subgroups. Of these, one branch included seven patients whose gene expression profile resembled that of acute myeloid leukemia. These cases were characterized by over-expression of a large set of myeloid-related genes for surface antigens, transcription factors and granule proteins. Real-time quantitative polymerase chain reaction analysis confirmed over-expression of MPO, CEBPA, CEBPB, GRN and IL8. We, therefore, evaluated the expression levels of miR-223, involved in myeloid differentiation: these cases had significantly higher levels of miR-223 than had the other cases of T-cell acute lymphoblastic leukemia, with values comparable to those observed in acute myeloid leukemia. Finally, these patients appear to have an unfavorable clinical course. Using gene profiling we identified a subset of adult T-cell acute lymphoblastic leukemia, accounting for 10% of the cases analyzed, which displays myeloid features. These cases were not recognized by standard approaches, underlining the importance of gene profiling in identifying novel acute leukemia subsets. The recognition of this subgroup may have clinical, prognostic and therapeutic implications.Haematologica 04/2010; 95(7):1114-21. · 6.42 Impact Factor -
Article: Heterochromatin protein 1 (HP1a) positively regulates euchromatic gene expression through RNA transcript association and interaction with hnRNPs in Drosophila.
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ABSTRACT: Heterochromatin Protein 1 (HP1a) is a well-known conserved protein involved in heterochromatin formation and gene silencing in different species including humans. A general model has been proposed for heterochromatin formation and epigenetic gene silencing in different species that implies an essential role for HP1a. According to the model, histone methyltransferase enzymes (HMTases) methylate the histone H3 at lysine 9 (H3K9me), creating selective binding sites for itself and the chromodomain of HP1a. This complex is thought to form a higher order chromatin state that represses gene activity. It has also been found that HP1a plays a role in telomere capping. Surprisingly, recent studies have shown that HP1a is present at many euchromatic sites along polytene chromosomes of Drosophila melanogaster, including the developmental and heat-shock-induced puffs, and that this protein can be removed from these sites by in vivo RNase treatment, thus suggesting an association of HP1a with the transcripts of many active genes. To test this suggestion, we performed an extensive screening by RIP-chip assay (RNA-immunoprecipitation on microarrays), and we found that HP1a is associated with transcripts of more than one hundred euchromatic genes. An expression analysis in HP1a mutants shows that HP1a is required for positive regulation of these genes. Cytogenetic and molecular assays show that HP1a also interacts with the well known proteins DDP1, HRB87F, and PEP, which belong to different classes of heterogeneous nuclear ribonucleoproteins (hnRNPs) involved in RNA processing. Surprisingly, we found that all these hnRNP proteins also bind heterochromatin and are dominant suppressors of position effect variegation. Together, our data show novel and unexpected functions for HP1a and hnRNPs proteins. All these proteins are in fact involved both in RNA transcript processing and in heterochromatin formation. This suggests that, in general, similar epigenetic mechanisms have a significant role on both RNA and heterochromatin metabolisms.PLoS Genetics 10/2009; 5(10):e1000670. · 8.69 Impact Factor -
Article: Role of microRNAs in hematological malignancies.
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ABSTRACT: microRNAs (miRNAs) are short noncoding RNAs that function as post-transcriptional negative regulators of gene expression. They have been shown to be involved in the control of cell proliferation and differentiation, as well as acting as oncogenes or tumor-suppressor genes, suggesting their involvement in cancer development and progression. Expression profiles of human miRNAs have shown that many of them are aberrantly expressed in hematological malignancies. Therefore, miRNA profiling may be useful to distinguish between normal and tumor cells, and to create signatures for a variety of leukemia subtypes. Here, we review recent evidence for the involvement of miRNAs in the pathogenesis of different hematopoietic malignancies and their potential applications in diagnosis, prognosis and therapy of human leukemia.Expert Review of Hematology 08/2009; 2(4):415-23. · 1.16 Impact Factor -
Article: NFI-A directs the fate of hematopoietic progenitors to the erythroid or granulocytic lineage and controls beta-globin and G-CSF receptor expression.
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ABSTRACT: It is generally conceded that selective combinations of transcription factors determine hematopoietic lineage commitment and differentiation. Here we show that in normal human hematopoiesis the transcription factor nuclear factor I-A (NFI-A) exhibits a marked lineage-specific expression pattern: it is upmodulated in the erythroid (E) lineage while fully suppressed in the granulopoietic (G) series. In unilineage E culture of hematopoietic progenitor cells (HPCs), NFI-A overexpression or knockdown accelerates or blocks erythropoiesis, respectively: notably, NFI-A overexpression restores E differentiation in the presence of low or minimal erythropoietin stimulus. Conversely, NFI-A ectopic expression in unilineage G culture induces a sharp inhibition of granulopoiesis. Finally, in bilineage E + G culture, NFI-A overexpression or suppression drives HPCs into the E or G differentiation pathways, respectively. These NFI-A actions are mediated, at least in part, by a dual and opposite transcriptional action: direct binding and activation or repression of the promoters of the beta-globin and G-CSF receptor gene, respectively. Altogether, these results indicate that, in early hematopoiesis, the NFI-A expression level acts as a novel factor channeling HPCs into either the E or G lineage.Blood 07/2009; 114(9):1753-63. · 9.90 Impact Factor -
Article: Role of microRNAs in myeloid differentiation.
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ABSTRACT: All types of blood cell of the body are continuously produced by rare pluripotent self-renewing HSCs (haemopoietic stem cells) by a process known as haemopoiesis. This process provides a valuable model for examining how genetic programmes involved in cell differentiation are established, and also how cell-fate specification is altered in leukaemia. Here, we describe examples of how miRNAs (microRNAs) can influence myelopoiesis and how the identification of their target mRNAs has contributed to the understanding of the molecular networks involved in the alternative control between cell growth and differentiation. Ectopic expression and knockdown of specific miRNAs have provided powerful molecular tools able to control the switch between proliferation and differentiation, therefore providing new therapeutic tools for interfering with tumorigenesis.Biochemical Society Transactions 01/2009; 36(Pt 6):1201-5. · 3.71 Impact Factor -
Article: Isolation and characterization of CD146+ multipotent mesenchymal stromal cells.
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ABSTRACT: Mesenchymal stromal cells (MSCs) represent a bone marrow (BM) population, classically defined by five functional properties: extensive proliferation, ability to differentiate into osteoblasts, chondrocytes, adipocytes, and stromal cells-supporting hematopoiesis. However, research progress in this area has been hampered by lack of suitable markers and standardized procedures for MSC isolation. We have isolated a CD146(+) multipotent MSC population from 20 human BM donors displaying the phenotype of self-renewing osteoprogenitors; an extensive 12-week proliferation; and the ability to differentiate in osteoblasts, chondrocytes, adipocytes, and stromal cells supporting hematopoiesis. Furthermore, the CD146(+) MSCs secrete a complex combination of growth factors (GFs) controlling hematopoietic stem cells (HSCs) function, while providing a >2-log increase in the long-term culture (LTC) colony output in 8-week LTC over conventional assays. The hematopoietic stromal function exhibited by the MSCs was further characterized by manipulating LTCs with the chemical inhibitors Imatinib or SU-5416, targeting two GF receptors (GFRs), KIT or VEGFR2/1, respectively. Both treatments similarly impaired LTC colony output, indicating key roles for these two GF/GFR interactions to support LTC-initiating cell activity. CD146(+) MSCs may thus represent a tool to explore the MSC-HSC cross-talk in an in vitro surrogate model for HSC "niches," and for regenerative therapy studies. In addition, the MSC microRNA (miRNA) expression profile was analyzed by microarrays in both basic conditions and chondrogenic differentiation. Our analysis revealed that several miRNAs are modulated during chondrogenesis, and many of their putative targets are genes involved in chondrogenic differentiation.Experimental Hematology 08/2008; 36(8):1035-46. · 2.90 Impact Factor -
Article: Yeast Rrp14p is required for ribosomal subunit synthesis and for correct positioning of the mitotic spindle during mitosis.
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ABSTRACT: Here we report that Rrp14p/Ykl082p is associated with pre-60S particles and to a lesser extent with earlier 90S pre-ribosomes. Depletion of Rrp14p inhibited pre-rRNA synthesis on both the 40S and 60S synthesis pathways. Synthesis of the 20S precursor to the 18S rRNA was largely blocked, as was maturation of the 27SB pre-rRNA to the 5.8S and 25S rRNAs. Unexpectedly, Rrp14p-depleted cells also showed apparently specific cell-cycle defects. Following release from synchronization in S phase, Rrp14p-depleted cells uniformly arrested in metaphase with short mitotic spindles that were frequently incorrectly aligned with the site of bud formation. In the absence of Bub2p, which is required for the spindle orientation checkpoint, this metaphase arrest was not seen in Rrp14p-depleted cells, which then arrested with multiple buds, several SPBs and binucleate mother cells. These data suggest that Rrp14p may play some role in cell polarity and/or spindle positioning, in addition to its function in ribosome synthesis.Nucleic Acids Research 02/2007; 35(4):1354-66. · 8.03 Impact Factor -
Article: Microarray detection of novel nuclear RNA substrates for the exosome.
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ABSTRACT: Microarray analyses were performed on yeast strains mutant for the nuclear-specific exosome components Rrp6p and Rrp47p/Lrp1p or the core component Rrp41p/Ski6p, at permissive temperature and following transfer to 37 degrees C. 339 mRNAs showed clearly altered expression levels, with an unexpectedly high degree of heterogeneity in the different exosome mutants. In contrast, no clear alterations were seen in strains lacking the cytoplasmic exosome component Ski7p. 27 mRNAs that were overexpressed in each strain defective in the nuclear exosome are good candidates for regulation by nuclear turnover. These included the mRNA for the autoregulated RNA-binding protein Nrd1p. Northern and primer extension analyses confirmed the elevated NRD1 mRNA levels in exosome mutants, and revealed the accumulation of truncated 5' fragments of the mRNA. These contain a predicted Nrd1p-binding site, potentially sequestering the protein and disrupting its autoregulation. Several genes located immediately downstream of independently transcribed snoRNA genes were overexpressed in exosome mutants, presumably due to stabilization of the products of transcription termination read-through. Further analyses indicated that many snoRNA and snRNA genes are inefficiently terminated, but read-through transcripts into downstream ORFs are normally rapidly degraded by the exosome.Yeast 05/2006; 23(6):439-54. · 1.89 Impact Factor -
Article: A minicircuitry comprised of microRNA-223 and transcription factors NFI-A and C/EBPalpha regulates human granulopoiesis.
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ABSTRACT: MicroRNAs play important roles in cell differentiation by acting as translational inhibitors of specific target genes. Here we show that human granulocytic differentiation is controlled by a regulatory circuitry involving miR-223 and two transcriptional factors, NFI-A and C/EBPalpha. The two factors compete for binding to the miR-223 promoter: NFI-A maintains miR-223 at low levels, whereas its replacement by C/EBPalpha, following retinoic acid (RA)-induced differentiation, upregulates miR-223 expression. The competition by C/EBPalpha and the granulocytic differentiation are favored by a negative-feedback loop in which miR-223 represses NFI-A translation. In line with this, both RNAi against NFI-A and ectopic expression of miR-223 in acute promyelocytic leukemia (APL) cells enhance differentiation, whereas miR-223 knockdown inhibits the differentiation response to RA. Altogether, our data indicate that miR-223 plays a crucial role during granulopoiesis and point to the NFI-A repression as an important molecular pathway mediating gene reprogramming in this cell lineage.Cell 01/2006; 123(5):819-31. · 32.40 Impact Factor -
Article: The cotranscriptional assembly of snoRNPs controls the biosynthesis of H/ACA snoRNAs in Saccharomyces cerevisiae.
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ABSTRACT: The carboxy-terminal domain (CTD) of RNA polymerase II large subunit acts as a platform to assemble the RNA processing machinery in a controlled way throughout the transcription cycle. In yeast, recent findings revealed a physical connection between phospho-CTD, generated by the Ctk1p kinase, and protein factors having a function in small nucleolar RNA (snoRNA) biogenesis. The snoRNAs represent a large family of polymerase II noncoding transcripts that are associated with highly conserved polypeptides to form stable ribonucleoprotein particles (snoRNPs). In this work, we have studied the biogenesis of the snoRNPs belonging to the box H/ACA class. We report that the assembly factor Naf1p and the core components Cbf5p and Nhp2p are recruited on H/ACA snoRNA genes very early during transcription. We also show that the cotranscriptional recruitment of Naf1p and Cbf5p is Ctk1p dependent and that Ctk1p and Cbf5p are required for preventing the readthrough into the snoRNA downstream genes. All these data suggest that proper cotranscriptional snoRNP assembly controls 3'-end formation of snoRNAs and, consequently, the release of a functional particle.Molecular and Cellular Biology 08/2005; 25(13):5396-403. · 5.53 Impact Factor -
Article: Rrp15p, a novel component of pre-ribosomal particles required for 60S ribosome subunit maturation.
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ABSTRACT: In eukaryotes ribosome biogenesis required that rRNAs primary transcripts are assembled in pre-ribosomal particles and processed. Protein factors and pre-ribosomal complexes involved in this complex pathway are not completely depicted. The essential ORF YPR143W encodes in yeast for an uncharacterized protein product, named here Rrp15p. Cellular function of Rrp15p has not so far defined even if nucleolar location was referred. With the aim to define the possible role of this orphan gene, we performed TAP-tagging of Rrp15p and investigated its molecular association with known pre-ribosomal complexes. Comparative sucrose gradient sedimentation analyses of yeast lysates expressing the TAP-tagged Rrp15p, strongly indicated that this protein is a component of the pre-60S particles. Northern hybridization, primer extension and functional proteomics on TAP-affinity isolated complexes proved that Rrp15p predominately associated with pre-rRNAs and proteins previously characterized as components of early pre-60S ribosomal particles. Finally, depletion of Rrp15p inhibited the accumulation of 27S and 7S pre-rRNAs and 5.8S and 25S mature rRNA. These results provide the first indication that Rrp15p is a novel factor involved in the early maturation steps of the 60S subunits. Moreover, the identification of the protein kinase CK2 in the Rrp15p-containing pre-ribosomal particles here reported, sustains the link between ribosome synthesis and cell cycle progression.RNA 05/2005; 11(4):495-502. · 5.09 Impact Factor -
Article: PIN domain of Nob1p is required for D-site cleavage in 20S pre-rRNA.
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ABSTRACT: Nob1p (Yor056c) is essential for processing of the 20S pre-rRNA to the mature 18S rRNA. It is part of a pre-40S ribosomal particle that is transported to the cytoplasm and subsequently cleaved at the 3' end of mature 18S rRNA (D-site). Nob1p is also reported to participate in proteasome biogenesis, and it was therefore unclear whether its primary activity is in ribosome synthesis. In this work, we describe a homology model of the PIN domain of Nob1p, which structurally mimics Mg(2+)-dependent exonucleases despite negligible similarity in primary sequence. Insights gained from this model were used to design a point mutation that was predicted to abolish the postulated enzymatic activity. Cells expressing Nob1p with this mutation failed to cleave the 20S pre-rRNA. This supports both the significance of the structural model and the idea that Nob1p is the long-sought D-site endonuclease.RNA 12/2004; 10(11):1698-701. · 5.09 Impact Factor -
Article: Cic1p/Nsa3p is required for synthesis and nuclear export of 60S ribosomal subunits.
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ABSTRACT: Cic1p/Nsa3p was previously reported to be associated with the 26S proteasome and required for the degradation of specific substrates, but was also shown to be associated with early pre-60S particles and to be localized to the nucleolus. Here we report that Cic1p/Nsa3p is required for the synthesis of 60S ribosome subunits. A temperature-sensitive lethal cic1-2 point mutation inhibits synthesis of the mature 5.8S and 25S rRNAs. Release of the pre-60S particles from the nucleolus to the nucleoplasm was also inhibited as judged by the nuclear accumulation of an Rpl11b-GFP reporter construct. We suggest that Cic1p/Nsa3p associates early with nascent preribosomal particles and is required for correct processing and nuclear release of large ribosomal subunit precursors.RNA 01/2004; 9(12):1431-6. · 5.09 Impact Factor -
Article: Insights into the structure and function of a guide RNP.
Natural Structural Biology 05/2003; 10(4):237-9. -
Article: Nob1p is required for cleavage of the 3' end of 18S rRNA.
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ABSTRACT: We report the characterization of a novel factor, Nob1p (Yor056c), which is essential for the synthesis of 40S ribosome subunits. Genetic depletion of Nob1p strongly inhibits the processing of the 20S pre-rRNA to the mature 18S rRNA, leading to the accumulation of high levels of the 20S pre-rRNA together with novel degradation intermediates. 20S processing occurs within a pre-40S particle after its export from the nucleus to the cytoplasm. Consistent with a direct role in this cleavage, Nob1p was shown to be associated with the pre-40S particle and to be present in both the nucleus and the cytoplasm. This suggests that Nob1p accompanies the pre-40S ribosomes during nuclear export. Pre-40S export is not, however, inhibited by depletion of Nob1p.Molecular and Cellular Biology 04/2003; 23(5):1798-807. · 5.53 Impact Factor -
Article: Naf1 p is a box H/ACA snoRNP assembly factor.
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ABSTRACT: Box H/ACA small nucleolar ribonucleoprotein particles (snoRNPs) contain four essential proteins, Cbf5p, Gar1p, Nhp2p, and Nop10p, each of which, with the exception of Gar1p, is required for box H/ACA snoRNA accumulation. Database searches identified a novel essential protein, which we termed Naf1p, with a region of homology to the RNA-binding domain of Gar1p and other features in common with hnRNP-like proteins. Naf1p is localized to the nucleus and is not a stable component of the H/ACA snoRNPs, but it is required for the accumulation of all box H/ACA snoRNAs. This requirement is not at the level of snoRNA transcription initiation or termination. Naf1 p shows in vitro RNA-binding activity and also binds directly to Cbf5p and Nhp2p. Naf1p was shown to bind to the CTD in vivo in a two-hybrid assay, and the phosphorylated CTD, but not the nonphosphorylated CTD, was shown to precipitate tagged Naf1p from a cell lysate. We propose that Naf1 p is recruited to the CTD of RNA polymerase II and binds to nascent box H/ACA snoRNAs promoting snoRNP assembly.RNA 01/2003; 8(12):1502-14. · 5.09 Impact Factor -
Article: Purified box C/D snoRNPs are able to reproduce site-specific 2'-O-methylation of target RNA in vitro.
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ABSTRACT: Small nucleolar RNAs (snoRNAs) are associated in ribonucleoprotein particles localized to the nucleolus (snoRNPs). Most of the members of the box C/D family function in directing site-specific 2'-O-methylation of substrate RNAs. Although the selection of the target nucleotide requires the antisense element and the conserved box D or D' of the snoRNA, the methyltransferase activity is supposed to reside in one of the protein components. Through protein tagging of a snoRNP-specific factor, we purified to homogeneity box C/D snoRNPs from the yeast Saccharomyces cerevisiae. Mass spectrometric analysis demonstrated the presence of Nop1p, Nop58p, Nop56p, and Snu13p as integral components of the particle. We show that purified snoRNPs are able to reproduce the site-specific methylation pattern on target RNA and that the predicted S-adenosyl-L-methionine-binding region of Nop1p is responsible for the catalytic activity.Molecular and Cellular Biology 11/2002; 22(19):6663-8. · 5.53 Impact Factor -
Article: Making ribosomes.
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ABSTRACT: The past year has seen dramatic changes in our understanding of ribosome synthesis, fuelled largely by advances in proteomic analysis. It is now possible to outline the pathway of ribosome assembly, which is highly dynamic and involves a remarkable separation of the factors involved in the synthesis of the 40S and 60S ribosomal subunits. Around 140 identified, non-ribosomal proteins are currently implicated in post-transcriptional ribosome synthesis in yeast.Current Opinion in Cell Biology 07/2002; 14(3):313-8. · 12.90 Impact Factor
Top co-authors
Top Journals
- Molecular and Cellular Biology (5)
- RNA (4)
- Cell (1)
- The EMBO Journal (1)
- Experimental Hematology (1)
Institutions
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1995–2011
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Sapienza University of Rome
Roma, Latium, Italy
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2002–2007
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The University of Edinburgh
- Wellcome Trust Centre for Cell Biology
Edinburgh, SCT, United Kingdom
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