Publications (10)65.69 Total impact
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Article: Making alternative splicing decisions during epithelial-to-mesenchymal transition (EMT).
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ABSTRACT: Alternative splicing generates multiple mRNAs from a single transcript and is a major contributor to proteomic diversity and to the control of gene expression in complex organisms. Not surprisingly, this post-transcriptional event is tightly regulated in different tissues and developmental stages. An increasing body of evidences supports a causative role of aberrant alternative splicing in cancer. However, very little is known about its impact on cellular processes crucially involved in tumor progression. The aim of this review is to discuss the link between alternative splicing and the epithelial-to-mesenchymal transition (EMT), one of the major routes by which cancer cells acquire invasive capabilities and become metastatic. We begin with a brief overview of alternative splicing. Next, we discuss alternative splicing factors that regulate EMT. Finally, we provide examples of target genes presenting alternative splicing changes that contribute to the morphological conversions in the EMT process.Cellular and Molecular Life Sciences CMLS 02/2012; 69(15):2515-26. · 6.57 Impact Factor -
Article: Sam68 regulates EMT through alternative splicing-activated nonsense-mediated mRNA decay of the SF2/ASF proto-oncogene.
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ABSTRACT: Epithelial-to-mesenchymal transition (EMT) and its reversal (MET) are crucial cell plasticity programs that act during development and tumor metastasis. We have previously shown that the splicing factor and proto-oncogene SF2/ASF impacts EMT/MET through production of a constitutively active splice variant of the Ron proto-oncogene. Using an in vitro model, we now show that SF2/ASF is also regulated during EMT/MET by alternative splicing associated with the nonsense-mediated mRNA decay pathway (AS-NMD). Overexpression and small interfering RNA experiments implicate the splicing regulator Sam68 in AS-NMD of SF2/ASF transcripts and in the choice between EMT/MET programs. Moreover, Sam68 modulation of SF2/ASF splicing appears to be controlled by epithelial cell-derived soluble factors that act through the ERK1/2 signaling pathway to regulate Sam68 phosphorylation. Collectively, our results reveal a hierarchy of splicing factors that integrate splicing decisions into EMT/MET programs in response to extracellular stimuli.The Journal of Cell Biology 09/2010; 191(1):87-99. · 10.26 Impact Factor -
Article: Alternative splicing and tumor progression.
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ABSTRACT: Alternative splicing is a key molecular mechanism for increasing the functional diversity of the eukaryotic proteomes. A large body of experimental data implicates aberrant splicing in various human diseases, including cancer. Both mutations in cis-acting splicing elements and alterations in the expression and/or activity of splicing regulatory factors drastically affect the splicing profile of many cancer-associated genes. In addition, the splicing profile of several cancer-associated genes is altered in particular types of cancer arguing for a direct role of specific splicing isoforms in tumor progression. Deciphering the mechanisms underlying aberrant splicing in cancer may prove crucial to understand how splicing machinery is controlled and integrated with other cellular processes, in particular transcription and signaling pathways. Moreover, the characterization of splicing deregulation in cancer will lead to a better comprehension of malignant transformation. Cancer-associated alternative splicing variants may be new tools for the diagnosis and classification of cancers and could be the targets for innovative therapeutical interventions based on highly selective splicing correction approaches.Current Genomics 01/2009; 9(8):556-70. · 2.41 Impact Factor -
Article: Transcription of Satellite III non-coding RNAs is a general stress response in human cells.
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ABSTRACT: In heat-shocked human cells, heat shock factor 1 activates transcription of tandem arrays of repetitive Satellite III (SatIII) DNA in pericentromeric heterochromatin. Satellite III RNAs remain associated with sites of transcription in nuclear stress bodies (nSBs). Here we use real-time RT-PCR to study the expression of these genomic regions. Transcription is highly asymmetrical and most of the transcripts contain the G-rich strand of the repeat. A low level of G-rich RNAs is detectable in unstressed cells and a 10(4)-fold induction occurs after heat shock. G-rich RNAs are induced by a wide range of stress treatments including heavy metals, UV-C, oxidative and hyper-osmotic stress. Differences exist among stressing agents both for the kinetics and the extent of induction (>100- to 80.000-fold). In all cases, G-rich transcripts are associated with nSBs. On the contrary, C-rich transcripts are almost undetectable in unstressed cells and modestly increase after stress. Production of SatIII RNAs after hyper-osmotic stress depends on the Tonicity Element Binding Protein indicating that activation of the arrays is triggered by different transcription factors. This is the first example of a non-coding RNA whose transcription is controlled by different transcription factors under different growth conditions.Nucleic Acids Research 02/2008; 36(2):423-34. · 8.03 Impact Factor -
Article: Cell motility is controlled by SF2/ASF through alternative splicing of the Ron protooncogene.
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ABSTRACT: Ron, the tyrosine kinase receptor for the Macrophage-stimulating protein, is involved in cell dissociation, motility, and matrix invasion. DeltaRon, a constitutively active isoform that confers increased motility to expressing cells, is generated through the skipping of exon 11. We show that abnormal accumulation of DeltaRon mRNA occurs in breast and colon tumors. Skipping of exon 11 is controlled by a silencer and an enhancer of splicing located in the constitutive exon 12. The strength of the enhancer parallels the relative abundance of DeltaRon mRNA and depends on a sequence directly bound by splicing factor SF2/ASF. Overexpression and RNAi experiments demonstrate that SF2/ASF, by controlling the production of DeltaRon, activates epithelial to mesenchymal transition leading to cell locomotion. The effect of SF2/ASF overexpression is reverted by specific knockdown of DeltaRon mRNA. This demonstrates a direct link between SF2/ASF-regulated splicing and cell motility, an activity important for embryogenesis, tissue formation, and tumor metastasis.Molecular Cell 01/2006; 20(6):881-90. · 14.18 Impact Factor -
Article: A single polypyrimidine tract binding protein (PTB) binding site mediates splicing inhibition at mouse IgM exons M1 and M2.
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ABSTRACT: Splicing of mouse immunoglobulin (IgM) exons M1 and M2 is directed by two juxtaposed regulatory elements, an enhancer and an inhibitor, located within the M2 exon. A primary function of the enhancer is to counteract the inhibitor, allowing splicing to occur. Here we show that the inhibitor contains two binding sites for polypyrimidine tract binding protein (PTB). Mutational analysis indicates that only one of these sites is necessary and sufficient to direct splicing inhibition both in vitro and in vivo. We demonstrate that the difference in activity of the two sites is explained by proximity to the intron. We further show that the presence of the enhancer results in the disruption of the PTB-inhibitor interaction, enabling splicing to occur. In the absence of the enhancer, splicing can be artificially activated by immuno-inhibition of PTB. Collectively, our results indicate that a single PTB binding site can function as an inhibitor that regulates alternative splicing both in vitro and in vivo.RNA 06/2004; 10(5):787-94. · 5.09 Impact Factor -
Article: RNA recognition motif 2 directs the recruitment of SF2/ASF to nuclear stress bodies.
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ABSTRACT: Heat shock induces the transcriptional activation of large heterochromatic regions of the human genome composed of arrays of satellite III DNA repeats. A number of RNA-processing factors, among them splicing factor SF2/ASF, associate with these transcription factors giving rise to nuclear stress bodies (nSBs). Here, we show that the recruitment of SF2/ASF to these structures is mediated by its second RNA recognition motif. Amino acid substitutions in the first alpha-helix of this domain, but not in the beta-strand regions, abrogate the association with nSBs. The same mutations drastically affect the in vivo activity of SF2/ASF in the alternative splicing of adenoviral E1A transcripts. Sequence analysis identifies four putative high-affinity binding sites for SF2/ASF in the transcribed strand of the satellite III DNA. We have verified by gel mobility shift assays that the second RNA-binding domain of SF2/ASF binds at least one of these sites. Our analysis suggests that the recruitment of SF2/ASF to nSBs is mediated by a direct interaction with satellite III transcripts and points to the second RNA-binding domain of the protein as the major determinant of this interaction.Nucleic Acids Research 02/2004; 32(14):4127-36. · 8.03 Impact Factor -
Article: Altered expression of heterogeneous nuclear ribonucleoproteins and SR factors in human colon adenocarcinomas
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ABSTRACT: Alternative splicing is part of the expression program of a wide number of genes implicated in cell growth and differentiation. Although the oc currence of inappropriate alternative splicing in tumors has started to emerge, the underlying molecular mechanisms have been, thus far, largely unexplored. We have investigated the alternative splicing pattern of the t'1)44 gene in specimens of nonfamilial colon adenocarcinomas at different stages of tumor progression. In the same patients, we have assessed by Northern blotting analysis the mRNA levels of different heterogeneous nuclear ribonucleoproteins and SR factors, all involved in pre-mRNA splicing and, more in general, in mRNA maturation. The results of this analysis highlight a general rule for the mode of splicing of the ('1)44 pre-mRNA. Moreover, we found that the mRNA levels of different SR proteins in tumor specimens are different from, and usually lower than, those detected in samples of nonpathological tissue adjacent to the tumor. Quantitative analysis demonstrates that, in tumors, the mRNA levels of ASF, SRp40, SRp55, and SRp75, when normalized to those of heteroge neous nuclear ribonucleoprotein Al, are lower than those of SRp20 and SRp30. Interestingly, this reduction is more drastic in patients showing a more altered (1)44 splicing pattern and seems to be related to the pro pensity to develop métastases.CANCER RESEARCH. 01/1998; 58(58):5818-5824. -
Article: Pro-metastatic splicing of Ron proto-oncogene mRNA can be reversed: therapeutic potential of bifunctional oligonucleotides and indole derivatives.
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ABSTRACT: Alternative splicing is a key molecular mechanism for increasing the complexity of the human transcriptome. Nearly all human genes are regulated by alternative splicing and the deregulation of this process has a causative role in various human diseases, including cancer. The discovery that alternatively spliced isoforms of several genes are expressed selectively in tumor cells opened the exciting possibility that pharmacological treatment of aberrant splicing could lead to new anti-cancer therapeutic approaches. An alternatively spliced isoform of a scatter factor receptor and proto-oncogene, Ron, accumulates during tumor progression of epithelial tissues and is able to confer an invasive phenotype to the expressing cells. This isoform, called ΔRon, originates from skipping of exon 11, and this specific splicing event is controlled by the expression level of the splicing factor and proto-oncogene SF2/ASF. Over-expression of SF2/ASF, which occurs frequently in various human tumors, induces the production of ΔRon and activates the epithelial to mesenchymal transition (EMT), leading to increased cell motility. In this paper, we have used targeted oligonucleotide enhancers of splicing (TOES) to recruit positive splicing factors to Ron exon 11 and thereby stimulate its inclusion. As an alternative approach, we have used selected indole derivatives that target ASF/SF2 splicing activity. Both treatments correct aberrant ΔRon splicing, restoring the incorporation of Ron exon 11. Notably, indole derivatives are also able to affect the invasive phenotype of the cells. Thus, these treatments may have therapeutic applications for anti-cancer purposes.RNA biology 7(4):495-503. · 5.56 Impact Factor -
Article: Alternative splicing and muscular dystrophy.
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ABSTRACT: Alternative splicing of pre-mRNAs is a major contributor to proteomic diversity and to the control of gene expression in higher eukaryotic cells. For this reasons, alternative splicing is tightly regulated in different tissues and developmental stages and its disruption can lead to a wide range of human disorders. The aim of this review is to focus on the relevance of alternative splicing for muscle function and muscle disease. We begin by giving a brief overview of alternative splicing, muscle-specific gene expression and muscular dystrophy. Next, to illustrate these concepts we focus on two muscular dystrophy, myotonic muscular dystrophy and facioscapulohumeral muscular dystrophy, both associated to disruption of splicing regulation in muscle.RNA biology 7(4):441-52. · 5.56 Impact Factor
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- Nucleic Acids Research (2)
- RNA biology (2)
- Molecular Cell (1)
- RNA (1)
- Current Genomics (1)
Institutions
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2004–2012
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National Research Council
- Institute of Molecular Genetics IGM
Roma, Latium, Italy
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