The RNA-binding protein Sam68 contributes to proliferation and survival of human prostate cancer cells

Busà, Roberta; Paronetto, Maria Paola; Farini, Donatella; Pierantozzi, Enrico; Botti, Flavia; Angelini, Daniela F.; Attisani, F.; Vespasiani, Giuseppe; Sette, Claudio

doi:10.1038/sj.onc.1210224

Cited by 152 publications

(196 citation statements)

References 30 publications

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“…47,49,53 Previous data indicated that silencing of SND1 by small interfering RNAs (siRNAs) causes a significant decrease in PC3 cell growth. 43 As SAM68 was also shown to exert the same effect in the less-aggressive LNCaP cell line, 29 we first asked whether SND1 and SAM68 cooperate in supporting PCa cell proliferation. Transient knockdown of SND1 and SAM68 by RNAi in PC3 cells efficiently reduced the expression levels of both proteins at 48 h after transfection (Supplementary Figure S6A).…”

Section: Snd1 and Alternative Splicing M Cappellari Et Almentioning

confidence: 99%

“…Sequences for SAM68 siRNA were previously described. 29 The SND1 siRNA used was: 5 0 -UCUUUCUUCUGCUUUGCGG-3 0 . Scrambled siRNA was: 5 0 -GUGCUCAA UUGGAUUCUCU-3 0 .…”

Section: Sam68mentioning

confidence: 99%

“…[26][27][28] Moreover, SAM68 displays pro-oncogenic functions and is frequently upregulated in human cancer types, 17 including prostate cancer (PCa), wherein it supports cell proliferation and survival to genotoxic stresses. 29,30 In spite of the increasing number of studies reporting a role of SAM68 in human cancer, 17,31 the mechanism(s) of action of this protein in neoplastic cells is still largely unknown. As the activity and subcellular localization of SAM68 is influenced by its interaction with other proteins, 32,33 in the present work we set out to identify proteins that may affect SAM68 activity in PCa cells.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Snd1 and Alternative Splicing M Cappellari Et Almentioning

confidence: 99%

“…Sequences for SAM68 siRNA were previously described. 29 The SND1 siRNA used was: 5 0 -UCUUUCUUCUGCUUUGCGG-3 0 . Scrambled siRNA was: 5 0 -GUGCUCAA UUGGAUUCUCU-3 0 .…”

Section: Sam68mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2013

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“…On the other hand, acetylation of lysine residues by histone acetyltransferases enhances RNA binding (11). Finally, overexpression of Sam68 has been linked to prostate cancer, cell proliferation, and survival (12).…”

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confidence: 99%

Structural Basis for Homodimerization of the Src-associated during Mitosis, 68-kDa Protein (Sam68) Qua1 Domain

Meyer

Tripsianes

Vincendeau

et al. 2010

Journal of Biological Chemistry

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Sam68 (Src-associated during mitosis, 68 kDa) is a prototypical member of the STAR (signal transducer and activator of RNA) family of RNA-binding proteins. STAR proteins bind mRNA targets and modulate cellular processes such as cell cycle regulation and tissue development in response to extracellular signals. Sam68 has been shown to modulate alternative splicing of the pre-mRNAs of CD44 and Bcl-xL, which are linked to tumor progression and apoptosis. Sam68 and other STAR proteins recognize bipartite RNA sequences and are thought to function as homodimers. However, the structural and functional roles of the self-association are not known. Here, we present the solution structure of the Sam68 Qua1 homodimerization domain. Each monomer consists of two antiparallel ␣-helices connected by a short loop. The two subunits are arranged perpendicular to each other in an unusual four-helix topology. Mutational analysis of Sam68 in vitro and in a cell-based assay revealed that the Qua1 domain and residues within the dimerization interface are essential for alternative splicing of a CD44 minigene. Together, our results indicate that the Qua1 homodimerization domain is required for regulation of alternative splicing by Sam68. Sam682 (Src-associated during mitosis, 68 kDa) (1) belongs to the STAR (signal transducer and activator of RNA) family of RNAbinding proteins, which also includes Qk1 (quaking 1), SF1 (splicing factor 1), and Gld-1 (germline development defective-1) (2). STAR family proteins link signaling pathways and many aspects of RNA metabolism (splicing, localization, and translation). They are regulated by post-translational modifications such as phosphorylation, acetylation, and arginine methylation (2).Sam68 acts in post-transcriptional regulation of pre-mRNA splicing in response to extracellular signals (3). It is involved in a variety of pathways, including insulin and T-cell receptor signaling (4), and plays a key role in cell cycle regulation (5). Sam68 exhibits binding specificity for homopolymeric poly(U) RNA and has been shown to recognize UAAA or UUUA sequences with high affinity as determined by Systematic Evolution of Ligands by EXponential Enrichment (SELEX) and in vivo crosslinking (6, 7). Post-translational modifications can regulate Sam68 function by critically affecting the accessibility to RNA (8, 9). Tyrosine phosphorylation by Src kinase during mitosis enhances the interaction of Sam68 with Ras-GAP (10) but prevents its association with RNA. On the other hand, acetylation of lysine residues by histone acetyltransferases enhances RNA binding (11). Finally, overexpression of Sam68 has been linked to prostate cancer, cell proliferation, and survival (12).Sam68 has been identified as a key determinant in the alternative splicing of various important RNA targets, like CD44 (13) and Bcl-x L (14), which are linked to apoptosis and cancer. In particular, alternative splicing of CD44 impacts embryonic development and immune response (15-18). Up to 10 variant exon sequences can be included in the mature C...

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“…(b) SAM68 KH-type RNA-binding proteins are intriguing molecules that regulate the differentiation and function of several cell types and influence tumour development (Busa et al 2007;. A well-studied member of this family, SAM68, is a ubiquitously expressed factor that regulates many steps of RNA metabolism, including alternative mRNA splicing, nuclear mRNA export and translation.…”

Section: Rna-binding Proteins That Regulate Spermatogenesismentioning

confidence: 99%

Transcription and post-transcriptional regulation of spermatogenesis

Bettegowda

Wilkinson

2010

Phil. Trans. R. Soc. B

143

101

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Spermatogenesis in mammals is achieved by multiple players that pursue a common goal of generating mature spermatozoa. The developmental processes acting on male germ cells that culminate in the production of the functional spermatozoa are regulated at both the transcription and posttranscriptional levels. This review addresses recent progress towards understanding such regulatory mechanisms and identifies future challenges to be addressed in this field. We focus on transcription factors, chromatin-associated factors and RNA-binding proteins necessary for spermatogenesis and/ or sperm maturation. Understanding the molecular mechanisms that govern spermatogenesis has enormous implications for new contraceptive approaches and treatments for infertility.

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The RNA-binding protein Sam68 contributes to proliferation and survival of human prostate cancer cells

Cited by 152 publications

References 30 publications

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

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

Structural Basis for Homodimerization of the Src-associated during Mitosis, 68-kDa Protein (Sam68) Qua1 Domain

Transcription and post-transcriptional regulation of spermatogenesis

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