The emerging role of splicing factors in cancer

Grosso, Ana Rita; Martins, Sandra; Carmo‐Fonseca, Maria

doi:10.1038/embor.2008.189

Cited by 163 publications

(135 citation statements)

References 48 publications

(37 reference statements)

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“…Recent studies have shown an association between altered splicing machinery and cancers. 19,20 Dysregulation of splicing has been reported as an important factor in leukemia. [21][22][23] Alterations in spliceosome associated genes/proteins can significantly impact alternative splicing events like exon skipping or intron retention as reported in breast cancer, lung adenocarcinoma and chronic lymphocytic leukemia.…”

Section: Discussionmentioning

confidence: 99%

Dysregulation of splicing proteins in head and neck squamous cell carcinoma

Radhakrishnan

Nanjappa

Raja

et al. 2016

Cancer Biology & Therapy

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ABSRTRACTSignaling plays an important role in regulating all cellular pathways. Altered signaling is one of the hallmarks of cancers. Phosphoproteomics enables interrogation of kinase mediated signaling pathways in biological systems. In cancers, this approach can be utilized to identify aberrantly activated pathways that potentially drive proliferation and tumorigenesis. To identify signaling alterations in head and neck squamous cell carcinoma (HNSCC), we carried out proteomic and phosphoproteomic analysis of HNSCC cell lines using a combination of tandem mass tag (TMT) labeling approach and titanium dioxide-based enrichment. We identified 4,920 phosphosites corresponding to 2,212 proteins in six HNSCC cell lines compared to a normal oral cell line. Our data indicated significant enrichment of proteins associated with splicing. We observed hyperphosphorylation of SRSF protein kinase 2 (SRPK2) and its downstream substrates in HNSCC cell lines. SRPK2 is a splicing kinase, known to phosphorylate serine/arginine (SR) rich domain proteins and regulate splicing process in eukaryotes. Although genome-wide studies have reported the contribution of alternative splicing events of several genes in the progression of cancer, the involvement of splicing kinases in HNSCC is not known. In this study, we studied the role of SRPK2 in HNSCC. Inhibition of SRPK2 resulted in significant decrease in colony forming and invasive ability in a panel of HNSCC cell lines. Our results indicate that phosphorylation of SRPK2 plays a crucial role in the regulation of splicing process in HNSCC and that splicing kinases can be developed as a new class of therapeutic target in HNSCC.

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Section: Discussionmentioning

confidence: 99%

Dysregulation of splicing proteins in head and neck squamous cell carcinoma

Radhakrishnan

Nanjappa

Raja

et al. 2016

Cancer Biology & Therapy

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“…RBPs are essential factors in RNA metabolism and their aberrant expression or regulation profoundly affects the gene expression profile of cancer cells. [14][15][16] An example of RBP that is upregulated in several human tumors is SAM68 (Src-associated in mitosis of 68 kDa), a member of the STAR (Signal Transduction Activator of RNA metabolism) family of RBPs. 17 SAM68 is involved in regulating several aspects of RNA processing, such as transcription, [18][19][20][21] AS [22][23][24][25] and translation of cellular mRNAs.…”

Section: Introductionmentioning

confidence: 99%

The transcriptional co-activator SND1 is a novel regulator of alternative splicing in prostate cancer cells

et al. 2013

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Splicing abnormalities have profound impact in human cancer. Several splicing factors, including SAM68, have pro-oncogenic functions, and their increased expression often correlates with human cancer development and progression. Herein, we have identified using mass spectrometry proteins that interact with endogenous SAM68 in prostate cancer (PCa) cells. Among other interesting proteins, we have characterized the interaction of SAM68 with SND1, a transcriptional co-activator that binds spliceosome components, thus coupling transcription and splicing. We found that both SAM68 and SND1 are upregulated in PCa cells with respect to benign prostate cells. Upregulation of SND1 exerts a synergic effect with SAM68 on exon v5 inclusion in the CD44 mRNA. The effect of SND1 on CD44 splicing required SAM68, as it was compromised after knockdown of this protein or mutation of the SAM68-binding sites in the CD44 pre-mRNA. More generally, we found that SND1 promotes the inclusion of CD44 variable exons by recruiting SAM68 and spliceosomal components on CD44 pre-mRNA. Inclusion of the variable exons in CD44 correlates with increased proliferation, motility and invasiveness of cancer cells. Strikingly, we found that knockdown of SND1, or SAM68, reduced proliferation and migration of PCa cells. Thus, our findings strongly suggest that SND1 is a novel regulator of alternative splicing that promotes PCa cell growth and survival.Oncogene advance online publication, 2 September 2013; doi:10.1038/onc.2013.360Keywords: alternative splicing; SND1; SAM68; CD44; prostate cancer INTRODUCTION Nuclear processing of pre-mRNAs requires tightly regulated steps that ultimately yield a mature and functional mRNA. Splicing is the step that insures the removal of long non-coding sequences (introns) from the pre-mRNA and the joining of the exons. This phenomenon is driven by a large macromolecular complex, the spliceosome, composed of five small nuclear ribonucleoproteins (snRNPs) and over 200 auxiliary proteins. 1 In higher eukaryotes, a large number of exons can be alternatively spliced to yield different transcripts from a single gene, thereby increasing the coding potential of the genome. 2,3 Indeed, the large majority of multi-exon human genes undergo alternative splicing (AS) to produce at least two mRNA variants. 4,5 As regulation of AS profoundly influences physiological and pathological processes, 3,6 the full comprehension of the molecular mechanisms regulating this step of pre-mRNA processing is of fundamental importance.Splicing is physically and functionally coupled to transcription. 7-10 Two models have been proposed for how transcription might affect changes in AS patterns. The 'recruitment model' suggests that the transcription apparatus physically interacts with splicing regulators, thereby affecting splicing decisions. The C-terminal domain (CTD) of the largest subunit of the RNA polymerase II (RNAPII) has a central role in this coupling process by favoring the recruitment of RNA processing factors on the nascent transcripts. 9,10 ...

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“…There is growing evidence that splicing and splicing factors are also dysregulated in many forms of human cancers (24). To determine which of them is involved E6 splicing, we focused our attention on hnRNPA1 and A2, ASF/SF2, Sam68, and Brm (6), which are all expressed in HPV16 immortalized keratinocytes (Fig.…”

Section: Egf-directed Alternative Splicing Of Hpv16 E6 Is Mediated Bymentioning

confidence: 99%

Alternative splicing of human papillomavirus type-16 E6/E6* early mRNA is coupled to EGF signaling via Erk1/2 activation

Rosenberger

Arce

Langbein

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Certain types of human papillomaviruses (HPVs) are etiologically linked to cervical cancer. Their transforming capacity is encoded by a polycistronic premRNA, where alternative splicing leads to the translation of functional distinct proteins such as E6, E6*, and E7. Here we show that splicing of HPV16 E6/E7 ORF cassette is regulated by the epidermal growth factor (EGF) pathway. The presence of EGF was coupled to preferential E6 expression, whereas depletion of EGF, or treatment with EGF receptor (EGFR) neutralizing antibodies or the EGFR inhibitor tyrphostin AG1478, resulted in E6 exon exclusion in favor of E6*. As a consequence, increased p53 levels and enhanced translation of E7 with a subsequent reduction of the retinoblastoma protein pRb could be discerned. E6 exon exclusion upon EGF depletion was independent from promoter usage, mRNA stability, or selective mRNA transport. Time-course experiments and incubation with cycloheximide demonstrated that E6 alternative splicing is a direct and reversible effect of EGF signal transduction, not depending on de novo protein synthesis. Within this process, Erk1/2-kinase activation was the critical event for E6 exon inclusion, mediated by the upstream MAP kinase MEK1/2. Moreover, siRNA knockdown experiments revealed an involvement of splicing factors hnRNPA1 and hnRNPA2 in E6 exon exclusion, whereas the splicing factors Brm and Sam68 were found to promote E6 exon inclusion. Because there is a natural gradient of EGF and EGF receptor expression in the stratified epithelium, it is reasonable to assume that EGF modulates E6/E7 splicing during the viral life cycle and transformation.P articular types of human papillomaviruses (HPVs) such as HPV16, 18, 31, and 33, respectively, are the etiological agents for the development of anogenital tumors. Their transforming potential is encoded by the viral oncoproteins E6 and E7, where among other functions, E6 labilizes p53 and prevents apoptosis, and E7 promotes cell cycle progression by degrading the retinoblastoma protein pRb (1). HPV gene transcription is regulated by two main promoters, the early p97 and the late p670 promoter (2). Activation of either promoter is regulated by differentiation, resulting in the synthesis of polycistronic mRNAs, which are further regulated by differential splicing (3, 4). For polycistronic mRNAs, it is known that only the first ORF is translated efficiently when intercistronic distances are short (5).Alternative splicing can be regulated dependent on the developmental stage or by extracellular stimuli, where an increasing number of pathways and splicing factors have been identified (6). For splicing reaction, the spliceosome recognizes exon-intron boundaries of the 5′-donor and 3′-acceptor splice site. Furthermore, specific sequence motifs within exons can positively or negatively influence the recognition of nearby splice sites (7). The activity of so-called exonic splicing enhancers or exonic splicing silencers can be modulated by splicing factors like SR proteins or hnRNPs, which in turn all...

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The emerging role of splicing factors in cancer

Cited by 163 publications

References 48 publications

Dysregulation of splicing proteins in head and neck squamous cell carcinoma

Dysregulation of splicing proteins in head and neck squamous cell carcinoma

The transcriptional co-activator SND1 is a novel regulator of alternative splicing in prostate cancer cells

Alternative splicing of human papillomavirus type-16 E6/E6* early mRNA is coupled to EGF signaling via Erk1/2 activation

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