scholarly journals PTBP2-dependent alternative splicing regulates protein transport and mitochondria morphology in post-meiotic germ cells.

2018 ◽  
Author(s):  
Molly M Hannigan ◽  
Hisashi Fujioka ◽  
Adina Brett-Morris ◽  
Jason A Mears ◽  
Donny D Licatalosi
Keyword(s):  
Alternative Splicing ◽  
Germ Cells ◽  
Protein Trafficking ◽  
Rna Splicing ◽  
Protein Transport ◽  
Rna Binding ◽  
Binding Protein ◽  
Polypyrimidine Tract Binding Protein ◽  
Alternative Mrna Splicing ◽  
Genes Encoding

The RNA binding protein PTBP2 (polypyrimidine tract binding protein 2) is a key regulator of tissue-specific alternative RNA splicing. In the testis, PTBP2 is expressed in meiotic and post-meiotic germ cells (spermatocytes and spermatids, respectively). In these cells, PTBP2 is required for proper alternative mRNA splicing for over 200 genes, disproportionately affecting genes encoding proteins involved in protein trafficking via transport vesicles. In this study, we used electron microscopy to test the hypothesis that protein trafficking is impaired in the absence of PTBP2, and to further investigate why spermatogenesis abruptly halts in PTBP2-deficient spermatids. Ultrastructural analysis shows that protein trafficking in spermatids is aberrant in the absence of PTBP2. Unexpectedly, we also found that mitochondria morphology and number are significantly altered in PTBP2-deficient spermatids, consistent with increased mitochondria fission. Furthermore, we show that genes with key roles in mitochondria dynamics and function are post-transcriptionally regulated by PTBP2 and in different stages of spermatogenesis. Collectively, the data provide ultrastructural evidence that alternative splicing regulation by PTBP2 during spermatogenesis is critical for proper regulation of protein trafficking and mitochondria morphology.

scholarly journals Solution and crystal structures of a C-terminal fragment of the neuronal isoform of the polypyrimidine tract binding protein (nPTB)

2014 ◽  
Author(s):  
Amar Joshi ◽  
Vicent Esteve ◽  
Adrian N Buckroyd ◽  
Markus Blatter ◽  
Frédéric HT Allain ◽  
...  
Keyword(s):  
Amino Acid ◽  
Rna Splicing ◽  
Messenger Rna ◽  
Solution Structure ◽  
Rna Binding ◽  
Binding Protein ◽  
Amino Acid Side Chain ◽  
Polypyrimidine Tract ◽  
Polypyrimidine Tract Binding ◽  
Polypyrimidine Tract Binding Protein

The eukaryotic polypyrimidine tract binding protein (PTB) serves primarily as a regulator of alternative splicing of messenger RNA, but is also co-opted to other roles such as RNA localisation and translation initiation from internal ribosome entry sites. The neuronal paralogue of PTB (nPTB) protein is 75% identical in amino acid sequence with PTB. Although the two proteins have broadly similar RNA binding specificities and effects on RNA splicing, differential expression of PTB and nPTB can lead to the generation of alternatively spliced mRNAs. RNA binding by PTB and nPTB is mediated by four RNA recognition motifs (RRMs). We present here the crystal and solution structures of the C-terminal domain of nPTB (nPTB34) which contains RRMs 3 and 4. As expected the structures are similar to each other and to the solution structure of the equivalent fragment from PTB (PTB34). The result confirms that, as found for PTB, RRMs 3 and 4 of nPTB interact with one another to form a stable unit that presents the RNA-binding surfaces of the component RRMs on opposing sides. The major differences between PTB34 and nPTB34 arise from amino acid side chain substitutions on the exposed β-sheet surfaces and adjoining loops of each RRM, which are likely to modulate interactions with RNA.

scholarly journals THE SPLICING FACTOR PTBP1 REPRESSES TP63 γ ISOFORM PRODUCTION IN SQUAMOUS CELL CARCINOMA

2021 ◽  
Author(s):  
William Taylor ◽  
David Reboutier ◽  
Luc Paillard ◽  
Agnes Mereau ◽  
Yann AUDIC
Keyword(s):  
Squamous Cell Carcinoma ◽  
Alternative Splicing ◽  
Cell Carcinoma ◽  
Squamous Cell ◽  
Rna Binding ◽  
Binding Protein ◽  
Negative Regulator ◽  
Mesenchymal Transition ◽  
Polypyrimidine Tract Binding Protein

The TP63 gene encodes the transcription factor p63. It is frequently amplified or overexpressed in squamous cell carcinomas. Owing to alternative splicing, p63 has multiple isoforms called α, β, γ and δ. The regulatory functions of p63 may be isoform-specific. The α isoform inhibits the epithelial to mesenchymal transition (EMT) and controls apoptosis, while the γ isoform promotes EMT. Here, we observed in TCGA data that a high ratio of the TP63γ isoform to the other isoforms is a pejorative factor for the survival of patients with head and neck squamous cell carcinoma (HNSCC). We therefore addressed the regulation of the γ isoform. In several tissues (GTEX data), the expression of the RNA-binding protein PTBP1 (polypyrimidine tract binding protein 1) is negatively correlated with the abundance of TP63γ. Accordingly, we demonstrated that PTBP1 depletion in HNSCC cell lines leads to an increase in abundance of the γ isoform. By RNA immunoprecipitation and in vitro interaction assays, we showed that PTBP1 directly binds to TP63 pre-mRNA in close proximity to the TP63γ-specific exon. The region around the TP63γ-specific exon was sufficient to elicit a PTBP1-dependent regulation of alternative splicing in a splice reporter minigene assay. Finally, we demonstrated that the regulation of TP63γ production by PTBP1 is conserved in amphibians, revealing that it encounters a strong evolutionary pressure. Together, these results identify TP63γ as a prognostic marker in HNSCC, and identify PTBP1 as a direct negative regulator of its production.

scholarly journals Solution and crystal structures of a C-terminal fragment of the neuronal isoform of the polypyrimidine tract binding protein (nPTB)

2014 ◽  
Author(s):  
Amar Joshi ◽  
Vicent Esteve ◽  
Adrian N Buckroyd ◽  
Markus Blatter ◽  
Frédéric HT Allain ◽  
...  
Keyword(s):  
Amino Acid ◽  
Rna Splicing ◽  
Messenger Rna ◽  
Solution Structure ◽  
Rna Binding ◽  
Binding Protein ◽  
Amino Acid Side Chain ◽  
Polypyrimidine Tract ◽  
Polypyrimidine Tract Binding ◽  
Polypyrimidine Tract Binding Protein

The eukaryotic polypyrimidine tract binding protein (PTB) serves primarily as a regulator of alternative splicing of messenger RNA, but is also co-opted to other roles such as RNA localisation and translation initiation from internal ribosome entry sites. The neuronal paralogue of PTB (nPTB) protein is 75% identical in amino acid sequence with PTB. Although the two proteins have broadly similar RNA binding specificities and effects on RNA splicing, differential expression of PTB and nPTB can lead to the generation of alternatively spliced mRNAs. RNA binding by PTB and nPTB is mediated by four RNA recognition motifs (RRMs). We present here the crystal and solution structures of the C-terminal domain of nPTB (nPTB34) which contains RRMs 3 and 4. As expected the structures are similar to each other and to the solution structure of the equivalent fragment from PTB (PTB34). The result confirms that, as found for PTB, RRMs 3 and 4 of nPTB interact with one another to form a stable unit that presents the RNA-binding surfaces of the component RRMs on opposing sides. The major differences between PTB34 and nPTB34 arise from amino acid side chain substitutions on the exposed β-sheet surfaces and adjoining loops of each RRM, which are likely to modulate interactions with RNA.

scholarly journals Pathway-guided analysis identifies Myc-dependent alternative pre-mRNA splicing in aggressive prostate cancers

2020 ◽  
Vol 117 (10) ◽  
pp. 5269-5279 ◽  
Author(s):  
John W. Phillips ◽  
Yang Pan ◽  
Brandon L. Tsai ◽  
Zhijie Xie ◽  
Levon Demirdjian ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Rna Splicing ◽  
Large Scale ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Mrna Splicing ◽  
Cancer Driver ◽  
Genes Encoding ◽  
Prostate Cancers

We sought to define the landscape of alternative pre-mRNA splicing in prostate cancers and the relationship of exon choice to known cancer driver alterations. To do so, we compiled a metadataset composed of 876 RNA-sequencing (RNA-Seq) samples from five publicly available sources representing a range of prostate phenotypes from normal tissue to drug-resistant metastases. We subjected these samples to exon-level analysis with rMATS-turbo, purpose-built software designed for large-scale analyses of splicing, and identified 13,149 high-confidence cassette exon events with variable incorporation across samples. We then developed a computational framework, pathway enrichment-guided activity study of alternative splicing (PEGASAS), to correlate transcriptional signatures of 50 different cancer driver pathways with these alternative splicing events. We discovered that Myc signaling was correlated with incorporation of a set of 1,039 cassette exons enriched in genes encoding RNA binding proteins. Using a human prostate epithelial transformation assay, we confirmed the Myc regulation of 147 of these exons, many of which introduced frameshifts or encoded premature stop codons. Our results connect changes in alternative pre-mRNA splicing to oncogenic alterations common in prostate and many other cancers. We also establish a role for Myc in regulating RNA splicing by controlling the incorporation of nonsense-mediated decay-determinant exons in genes encoding RNA binding proteins.

scholarly journals The RNA-binding protein ELAVL1/HuR is essential for mouse spermatogenesis, acting both at meiotic and postmeiotic stages

2011 ◽  
Vol 22 (16) ◽  
pp. 2875-2885 ◽  
Author(s):  
Mai Nguyen Chi ◽  
Jacques Auriol ◽  
Bernard Jégou ◽  
Dimitris L. Kontoyiannis ◽  
James M.A. Turner ◽  
...  
Keyword(s):  
Germ Cells ◽  
Posttranscriptional Regulation ◽  
Target Gene ◽  
Molecular Mechanisms ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
Female Sterility ◽  
Targeted Deletion

Posttranscriptional mechanisms are crucial to regulate spermatogenesis. Accurate protein synthesis during germ cell development relies on RNA binding proteins that control the storage, stability, and translation of mRNAs in a tightly and temporally regulated manner. Here, we focused on the RNA binding protein Embryonic Lethal Abnormal Vision (ELAV) L1/Human antigen R (HuR) known to be a key regulator of posttranscriptional regulation in somatic cells but the function of which during gametogenesis has never been investigated. In this study, we have used conditional loss- and gain-of-function approaches to address this issue in mice. We show that targeted deletion of HuR specifically in germ cells leads to male but not female sterility. Mutant males are azoospermic because of the extensive death of spermatocytes at meiotic divisions and failure of spermatid elongation. The latter defect is also observed upon HuR overexpression. To elucidate further the molecular mechanisms underlying spermatogenesis defects in HuR-deleted and -overexpressing testes, we undertook a target gene approach and discovered that heat shock protein (HSP)A2/HSP70-2, a crucial regulator of spermatogenesis, was down-regulated in both situations. HuR specifically binds hspa2 mRNA and controls its expression at the translational level in germ cells. Our study provides the first genetic evidence of HuR involvement during spermatogenesis and reveals Hspa2 as a target for HuR.

scholarly journals The RNA-binding protein Sam68 modulates the alternative splicing of Bcl-x

2007 ◽  
Vol 176 (7) ◽  
pp. 929-939 ◽  
Author(s):  
Maria Paola Paronetto ◽  
Tilman Achsel ◽  
Autumn Massiello ◽  
Charles E. Chalfant ◽  
Claudio Sette
Keyword(s):  
Alternative Splicing ◽  
Tyrosine Phosphorylation ◽  
Rna Binding ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
Live Cells ◽  
Hnrnp A1 ◽  
Splice Site Selection ◽  
Subnuclear Localization ◽  
Mrna Targets

The RNA-binding protein Sam68 is involved in apoptosis, but its cellular mRNA targets and its mechanism of action remain unknown. We demonstrate that Sam68 binds the mRNA for Bcl-x and affects its alternative splicing. Depletion of Sam68 by RNA interference caused accumulation of antiapoptotic Bcl-x(L), whereas its up-regulation increased the levels of proapoptotic Bcl-x(s). Tyrosine phosphorylation of Sam68 by Fyn inverted this effect and favored the Bcl-x(L) splice site selection. A point mutation in the RNA-binding domain of Sam68 influenced its splicing activity and subnuclear localization. Moreover, coexpression of ASF/SF2 with Sam68, or fusion with an RS domain, counteracted Sam68 splicing activity toward Bcl-x. Finally, Sam68 interacted with heterogenous nuclear RNP (hnRNP) A1, and depletion of hnRNP A1 or mutations that impair this interaction attenuated Bcl-x(s) splicing. Our results indicate that Sam68 plays a role in the regulation of Bcl-x alternative splicing and that tyrosine phosphorylation of Sam68 by Src-like kinases can switch its role from proapoptotic to antiapoptotic in live cells.

scholarly journals hnRNPH1 recruits PTBP2 and SRSF3 to cooperatively modulate alternative pre-mRNA splicing in germ cells and is essential for spermatogenesis and oogenesis

2021 ◽  
Author(s):  
Shuiqiao Yuan ◽  
Shenglei Feng ◽  
Jinmei Li ◽  
Hui Wen ◽  
Kuan Liu ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Germ Cell ◽  
Germ Cells ◽  
Rna Binding ◽  
Cell Development ◽  
Mrna Splicing ◽  
Conditional Knockout ◽  
Cell Junction ◽  
Germ Cell Development ◽  
Splicing Regulators

Abstract Coordinated regulation of alternative pre-mRNA splicing is essential for germ cell development. However, the molecular mechanism underlying that control alternative mRNA expression during germ cell development remains poorly understood. Herein, we showed that hnRNPH1, an RNA-binding protein, is highly expressed in the reproductive system and localized in the chromosomes of meiotic cells but excluded from the XY body in pachytene spermatocytes and recruits the splicing regulators PTBP2 and SRSF3 and cooperatively regulates the alternative splicing of the critical genes that are required for spermatogenesis. Conditional knockout Hnrnph1 in spermatogenic cells caused many abnormal splicing events that affect genes related to meiosis and communication between germ cells and Sertoli cells, characterized by asynapsis of chromosomes and impairment of germ-Sertoli communications, ultimately leading to male sterility. We further showed that hnRNPH1 could directly bind to SPO11 and recruit the splicing regulators PTBP2 and SRSF3 to regulate the alternative splicing of the target genes cooperatively. Strikingly, Hnrnph1 germline-specific mutant female mice were also infertile, and Hnrnph1-deficient oocytes exhibited a similar defective synapsis and cell-cell junction as shown in Hnrnph1-deficient male germ cells. Collectively, our data reveal an essential role for hnRNPH1 in regulating pre-mRNA splicing during spermatogenesis and oogenesis and support a molecular model whereby hnRNPH1 governs a network of alternative splicing events in germ cells via recruiting PTBP2 and SRSF3.

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