GO:0008187 poly-pyrimidine tract binding: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0008187 poly-pyrimidine tract binding is a molecular function defined as binding to a stretch of pyrimidines (cytosine or uracil) in an RNA molecule.
• The best-characterized poly-pyrimidine tract binding proteins are the PTBP family (PTBP1, PTBP2, PTBP3), which regulate alternative splicing, RNA stability and translation.
• PTBP1 interacts not only with RNA but also with a single-stranded DNA motif in a liver-specific enhancer, indicating broader nucleic-acid recognition roles.
• Poly-pyrimidine tract binding is essential for hematopoietic stem cell maintenance and red blood cell development by ensuring sufficient availability of ribosomal constituents.
• Alternative splicing regulation by poly-pyrimidine tract binding proteins is critical during myogenesis and in neuronal microexon splicing.
• Dysregulation of poly-pyrimidine tract binding is linked to myotonic dystrophy type 1 and other splicing-related pathologies.
Description
Poly-pyrimidine tract binding (GO:0008187) is a molecular function that enables a protein to recognize and bind stretches of pyrimidine nucleotides (cytosine or uracil) within an RNA molecule. This activity is fundamental to post-transcriptional gene regulation, as it allows RNA-binding proteins to dock onto specific transcripts and influence their processing, stability, localization and translation. The most extensively studied proteins carrying this function are the polypyrimidine tract binding proteins (PTBPs), including PTBP1, PTBP2 and PTBP3, which act as key regulators of alternative splicing. The functional importance of poly-pyrimidine tract binding extends beyond splicing; PTBP1 was shown to interact with a single-stranded DNA motif in a liver-specific enhancer, revealing that poly-pyrimidine recognition can also occur on DNA and contribute to transcriptional control. In addition, PTBP1 promotes hematopoietic stem cell maintenance and red blood cell development by ensuring sufficient availability of ribosomal constituents, linking this RNA-binding activity to ribosome biogenesis and hematopoiesis. Alternative splicing regulation by poly-pyrimidine tract binding proteins is also critical during myogenesis, where they coordinate the splicing of membrane trafficking genes. Neuronal-specific microexon splicing of TAF1 mRNA is directly regulated by SRRM4/nSR100, a process that intersects with poly-pyrimidine tract binding networks. Furthermore, SPF45/RBM17-dependent splicing in a distinct subset of human short introns highlights the diversity of splicing factors that cooperate with or compete for poly-pyrimidine tracts. Pharmacotherapy alleviates pathological changes in a human direct reprogrammed neuronal cell model of myotonic dystrophy type 1, a disease in which poly-pyrimidine tract binding dysregulation contributes to aberrant splicing. Understanding GO:0008187 is therefore essential for researchers studying RNA processing, hematopoiesis, muscle biology and neurological disorders.
poly-pyrimidine tract binding At A Glance
| GO ID | GO:0008187 |
|---|---|
| GO term | poly-pyrimidine tract binding |
| Ontology | molecular_function |
| Synonym | none |
| Major function | Binding to a stretch of pyrimidines (cytosine or uracil) in an RNA molecule |
| Major proteins | PTBP1, PTBP2, PTBP3, and other RRM-containing RNA-binding proteins |
| Substrate | Pyrimidine-rich RNA sequences (poly-C or poly-U tracts) |
| Associated processes | Alternative splicing, mRNA stability, translation, ribosome biogenesis |
| Disease relevance | Myotonic dystrophy type 1, cancer, hematopoietic disorders |
What Is GO:0008187?
According to the Gene Ontology, GO:0008187 poly-pyrimidine tract binding is defined as binding to a stretch of pyrimidines (cytosine or uracil) in an RNA molecule. This molecular function describes the selective interaction between a protein and pyrimidine-rich RNA sequences, which are often located in intronic regions near 3' splice sites or in other regulatory elements. The binding is mediated by RNA recognition motifs (RRMs) or other nucleic-acid-binding domains that recognize the pyrimidine-rich sequence with varying affinity depending on the surrounding ionic environment and sequence context.
Why Is poly-pyrimidine tract binding Important in Cell Biology?
Poly-pyrimidine tract binding is a central molecular function in post-transcriptional gene regulation. It governs the recruitment of splicing factors to 3' splice sites, modulates alternative splicing decisions, and influences mRNA stability and translation. Because pyrimidine-rich tracts are common in intronic and untranslated regions, proteins with this activity can shape the transcriptome and proteome of a cell. PTBP1, the archetypal poly-pyrimidine tract binding protein, is essential for hematopoietic stem cell maintenance and red blood cell development by ensuring sufficient availability of ribosomal constituents. Its role in alternative splicing regulation of membrane trafficking genes during myogenesis further underscores its importance in tissue differentiation. Dysregulation of poly-pyrimidine tract binding has been implicated in myotonic dystrophy type 1, where pharmacotherapy can alleviate pathological changes in neuronal cell models. Thus, GO:0008187 is a key node connecting RNA processing to development, differentiation and disease.
• Regulates alternative splicing by binding to pyrimidine-rich tracts near 3' splice sites.
• Essential for hematopoietic stem cell maintenance and red blood cell development.
• Controls alternative splicing of membrane trafficking genes during myogenesis.
• Involved in neuronal microexon splicing of TAF1 mRNA through SRRM4/nSR100.
• Cooperates with or competes with splicing factors such as SPF45/RBM17 in short introns.
• Linked to myotonic dystrophy type 1 pathology and potential pharmacological rescue.
• Can interact with single-stranded DNA motifs in liver-specific enhancers, expanding its regulatory scope.
• Modulated by monovalent ionic atmosphere, affecting selection of suboptimal RNA sequences.
• Relevant to retrotransposon biology, as shown for mouse VL30 elements.
• A target for CRISPR-based functional studies to dissect RNA-binding domains and disease mechanisms.
What Happens During poly-pyrimidine tract binding?
Recognition of pyrimidine-rich RNA sequences
In simple terms: The protein scans RNA and locks onto a stretch of C or U nucleotides.
The first step in poly-pyrimidine tract binding is the recognition of a pyrimidine-rich sequence within an RNA molecule. This recognition is typically mediated by RNA recognition motifs (RRMs) that form hydrogen bonds and stacking interactions with the pyrimidine bases. The binding affinity can be influenced by the ionic environment; monovalent ionic atmosphere modulates the selection of suboptimal RNA sequences by splicing factors' RNA recognition motifs. PTBP1, a prototypical poly-pyrimidine tract binding protein, was originally identified as a factor that interacts with a single-stranded DNA motif in a liver-specific enhancer, demonstrating that poly-pyrimidine recognition can also occur on DNA.
Recruitment of splicing machinery
In simple terms: Once bound, the protein helps assemble the splicing machinery on the RNA.
After binding to the pyrimidine tract, the protein recruits core splicing factors such as U2AF and other components of the spliceosome. However, some splicing events are independent of U2AF; for example, SPF45/RBM17-dependent splicing occurs in a distinct subset of human short introns, indicating that poly-pyrimidine tract binding proteins can function in alternative splicing pathways that do not rely on canonical U2AF. This step determines whether an exon is included or skipped, thereby regulating alternative splicing.
Regulation of alternative splicing outcomes
In simple terms: The binding event can switch exons on or off, creating different protein versions.
Poly-pyrimidine tract binding proteins such as PTBP1 and PTBP2 regulate alternative splicing of numerous genes. During myogenesis, alternative splicing regulation of membrane trafficking genes is controlled by these proteins. Neuronal-specific microexon splicing of TAF1 mRNA is directly regulated by SRRM4/nSR100, a process that intersects with poly-pyrimidine tract binding networks. These splicing decisions are critical for cell differentiation and tissue-specific gene expression.
Impact on RNA stability and translation
In simple terms: Binding can also affect how long the RNA lasts and how much protein is made.
Beyond splicing, poly-pyrimidine tract binding can influence mRNA stability and translation. PTBP1 promotes hematopoietic stem cell maintenance and red blood cell development by ensuring sufficient availability of ribosomal constituents, linking poly-pyrimidine tract binding to ribosome biogenesis and translation. This function is essential for maintaining the hematopoietic stem cell pool and supporting erythropoiesis.
Pathological consequences of dysregulation
In simple terms: When binding goes wrong, it can cause disease.
Dysregulation of poly-pyrimidine tract binding is associated with human disease. In myotonic dystrophy type 1, aberrant splicing due to poly-pyrimidine tract binding dysregulation contributes to pathological changes, and pharmacotherapy can alleviate these changes in a human direct reprogrammed neuronal cell model. Additionally, genomic analysis of mouse VL30 retrotransposons suggests that poly-pyrimidine tract binding may play a role in retrotransposon biology.
Key Genes Involved in GO:0008187 poly-pyrimidine tract binding
The following genes encode proteins that possess poly-pyrimidine tract binding activity or are directly involved in its regulatory network.
| Gene | Major Role | Research Relevance |
|---|---|---|
| PTBP1 | Binds pyrimidine-rich RNA tracts; regulates alternative splicing, mRNA stability and translation | Hematopoietic stem cell maintenance, red blood cell development, myogenesis, cancer |
| PTBP2 | Neuronal paralog of PTBP1; regulates alternative splicing in neurons | Neuronal differentiation, microexon splicing, brain development |
| PTBP3 | Regulates alternative splicing and RNA processing | Epithelial-mesenchymal transition, cancer progression |
| U2AF1 | Recognizes pyrimidine tract at 3' splice site; essential splicing factor | Splicing regulation, myelodysplastic syndromes |
| U2AF2 | Binds pyrimidine tract and interacts with U2AF1 | Constitutive and alternative splicing |
| SRSF1 | SR protein that binds pyrimidine-rich exonic sequences | Splicing regulation, cancer |
| SRSF2 | SR protein involved in splice site selection | Myelodysplastic syndromes, splicing fidelity |
| HNRNPA1 | Binds pyrimidine-rich sequences and regulates splicing | RNA metabolism, neurodegeneration |
| HNRNPC | Binds poly-U tracts and affects mRNA stability | RNA processing, cancer |
| RBM17 | SPF45/RBM17-dependent splicing in short introns | Alternative splicing, genome stability |
| SRRM4 | Regulates neuronal microexon splicing of TAF1 mRNA | Neuronal development, microexon regulation |
| TAF1 | Target of microexon splicing regulated by SRRM4/nSR100 | Neurological disorders, transcription initiation |
| CELF1 | RNA-binding protein that competes with PTBP1 for pyrimidine tracts | Myotonic dystrophy type 1 |
| MBNL1 | RNA-binding protein that regulates alternative splicing; antagonized by PTBP1 | Myotonic dystrophy type 1 |
| RBM39 | Splicing factor that interacts with poly-pyrimidine tracts | Cancer, splicing regulation |
| KHDRBS1 | Binds pyrimidine-rich sequences and regulates splicing | Signal transduction, RNA processing |
| TIA1 | Binds U-rich sequences and regulates splicing and translation | Stress granules, neurodegeneration |
| TIAL1 | Binds U-rich sequences and regulates RNA metabolism | Apoptosis, splicing |
How Is poly-pyrimidine tract binding Regulated?
Poly-pyrimidine tract binding is regulated at multiple levels. The expression levels of PTBP1 and its paralogs are controlled by developmental and tissue-specific cues; for example, PTBP1 is downregulated during neuronal differentiation to allow PTBP2 expression. Post-translational modifications such as phosphorylation can modulate the RNA-binding affinity of these proteins. The ionic environment also plays a role: monovalent ionic atmosphere modulates the selection of suboptimal RNA sequences by splicing factors' RNA recognition motifs. Additionally, competing RNA-binding proteins such as CELF1 and MBNL1 can antagonize or cooperate with poly-pyrimidine tract binding proteins, as seen in myotonic dystrophy type 1. In hematopoietic stem cells, PTBP1 ensures sufficient availability of ribosomal constituents, linking its regulation to ribosome biogenesis and cell growth.
poly-pyrimidine tract binding and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| PTBP1 | Hematopoietic stem cell maintenance and red blood cell development | Knockout mouse models, hematopoietic stem cell cultures |
| PTBP1 | Myotonic dystrophy type 1 | Human direct reprogrammed neuronal cell model |
| PTBP2 | Neuronal microexon splicing and neurodevelopment | Neuronal differentiation of iPSCs, knockout mice |
| RBM17 | Alternative splicing in short introns; cancer | Cancer cell lines with RBM17 knockout |
| CELF1 | Myotonic dystrophy type 1 | Patient-derived fibroblasts, neuronal models |
Myotonic dystrophy type 1
Myotonic dystrophy type 1 (DM1) is a multisystemic disorder caused by CTG repeat expansions in the DMPK gene. The expanded repeats sequester MBNL1 and lead to dysregulation of CELF1, resulting in aberrant alternative splicing. Poly-pyrimidine tract binding proteins, particularly PTBP1, contribute to the splicing changes observed in DM1. Pharmacotherapy alleviates pathological changes in a human direct reprogrammed neuronal cell model of myotonic dystrophy type 1, demonstrating that targeting splicing dysregulation can rescue disease phenotypes.
Hematopoietic disorders
PTBP1 promotes hematopoietic stem cell maintenance and red blood cell development by ensuring sufficient availability of ribosomal constituents. Dysregulation of this process can lead to hematopoietic stem cell exhaustion or ineffective erythropoiesis, contributing to bone marrow failure syndromes and anemias. Understanding poly-pyrimidine tract binding in hematopoietic cells may reveal therapeutic targets for these conditions.
Cancer
Poly-pyrimidine tract binding proteins are often overexpressed in cancer, where they promote proliferation, migration and survival by altering the splicing of genes involved in apoptosis, metabolism and metastasis. PTBP1 and PTBP3 have been implicated in various malignancies, making them potential targets for CRISPR-based functional studies and therapeutic intervention. The role of SPF45/RBM17-dependent splicing in short introns further highlights the complexity of splicing regulation in cancer cells.
Neurological disorders
Neuronal-specific microexon splicing of TAF1 mRNA is directly regulated by SRRM4/nSR100, a process that involves poly-pyrimidine tract binding networks. Disruption of microexon splicing has been linked to autism spectrum disorders and other neurodevelopmental conditions. Additionally, poly-pyrimidine tract binding proteins such as PTBP2 are critical for neuronal differentiation and function, and their dysregulation may contribute to neurodegeneration.
From poly-pyrimidine tract binding-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the role of PTBP1 in hematopoietic stem cell maintenance? | PTBP1 knockout mouse and hematopoietic stem cell transplantation assays |
| How does PTBP1 regulate alternative splicing during myogenesis? | C2C12 myoblast differentiation with PTBP1 knockdown or knockout |
| Does PTBP1 bind single-stranded DNA in liver-specific enhancers? | Liver-specific enhancer reporter assays and DNA-binding assays |
| What is the impact of PTBP1 dysregulation in myotonic dystrophy type 1? | Human direct reprogrammed neuronal cell model of DM1 |
| How do ionic conditions affect poly-pyrimidine tract binding? | In vitro RNA-binding assays with varying monovalent ion concentrations |
| What is the role of SPF45/RBM17 in short intron splicing? | Human cell lines with RBM17 knockout and short intron reporters |
How to Study the poly-pyrimidine tract binding Process
| Method | What It Measures | Typical Application |
|---|---|---|
| RIP-seq / CLIP-seq | Genome-wide RNA binding sites | Mapping poly-pyrimidine tracts bound by PTBP1 |
| RNA-seq with splicing analysis | Changes in alternative splicing | Quantifying exon inclusion upon PTBP1 knockout |
| EMSA / ITC | Binding affinity to RNA oligonucleotides | Measuring the effect of ionic conditions on binding |
| CRISPR knockout | Loss-of-function phenotypes | Studying PTBP1 in hematopoiesis |
| CRISPR point mutation | Dissecting RNA-binding domain function | Abolishing poly-pyrimidine binding in PTBP1 |
| CRISPR knock-in | Tagging endogenous proteins | Live-cell imaging of PTBP1 localization |
| Proteomics | Protein interaction partners | Identifying spliceosome components recruited by PTBP1 |
| Neuronal reprogramming | Disease modeling | Myotonic dystrophy type 1 neuronal model |
RNA immunoprecipitation and CLIP-seq
RNA immunoprecipitation (RIP) followed by sequencing (RIP-seq) or crosslinking and immunoprecipitation (CLIP-seq) allows genome-wide mapping of poly-pyrimidine tract binding sites. These methods identify the exact RNA sequences bound by PTBP1 and other proteins, revealing the repertoire of regulated transcripts. CLIP-seq has been instrumental in defining the RNA-binding landscape of PTBP1 in hematopoietic cells and neurons.
Alternative splicing analysis by RNA-seq
RNA sequencing (RNA-seq) combined with computational splicing analysis (e.g., rMATS, MAJIQ) quantifies changes in exon inclusion upon knockout or knockdown of poly-pyrimidine tract binding proteins. This approach has been used to demonstrate the role of PTBP1 in myogenesis and neuronal microexon splicing.
In vitro binding assays
Electrophoretic mobility shift assays (EMSA) and isothermal titration calorimetry (ITC) measure the binding affinity of purified RNA recognition motifs to pyrimidine-rich RNA oligonucleotides. These assays can be performed under varying ionic conditions to assess the effect of monovalent ions on sequence selection.
CRISPR-based functional genomics
CRISPR knockout, point mutation and knock-in models enable precise dissection of poly-pyrimidine tract binding protein domains and their physiological functions. For example, knocking out PTBP1 in hematopoietic stem cells can reveal its role in ribosome biogenesis and red blood cell development. Point mutations in the RNA recognition motif can abolish RNA binding and clarify its contribution to splicing regulation.
How CRISPR Can Be Used to Study GO:0008187 poly-pyrimidine tract binding
Knockout
CRISPR knockout of PTBP1 or other poly-pyrimidine tract binding proteins in cell lines or primary cells can reveal their essential functions. For example, PTBP1 knockout in hematopoietic stem cells impairs red blood cell development due to insufficient ribosomal constituents. Knockout models are also used to study alternative splicing changes during myogenesis.
Point Mutation
Point mutations in the RNA recognition motifs of PTBP1 can abolish poly-pyrimidine tract binding without affecting protein stability. These models help dissect the contribution of RNA binding to splicing regulation and cellular phenotypes. For instance, mutating key residues in the RRM domain can prevent binding to pyrimidine-rich tracts and alter splicing outcomes.
Knock-in
Knock-in of epitope tags (e.g., FLAG, HA) or fluorescent proteins (e.g., GFP) into the endogenous PTBP1 locus allows live-cell imaging and biochemical purification of the protein in its native context. Tagged knock-in models are valuable for CLIP-seq and proteomics studies to identify RNA targets and interaction partners.
Overexpression
Overexpression of PTBP1 or its paralogs in cell lines can mimic the elevated levels observed in cancer and other diseases. Overexpression models are used to study the effects of poly-pyrimidine tract binding on splicing, proliferation and migration. For example, overexpression of PTBP1 in neuronal cells can induce splicing changes similar to those seen in myotonic dystrophy type 1.
How EDITGENE Supports poly-pyrimidine tract binding Research
Researchers studying poly-pyrimidine tract binding-related genes often need to determine whether a candidate gene is causally involved in RNA processing, cellular differentiation or disease. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models, enabling functional validation of poly-pyrimidine tract binding proteins and their regulatory networks.
Contact EDITGENE today to design your custom CRISPR model for poly-pyrimidine tract binding research.
Frequently Asked Questions About poly-pyrimidine tract binding
What is poly-pyrimidine tract binding?
Poly-pyrimidine tract binding (GO:0008187) is a molecular function defined as binding to a stretch of pyrimidines (cytosine or uracil) in an RNA molecule. It is mediated by RNA-binding proteins such as PTBP1, which regulate alternative splicing and RNA metabolism.
What genes are involved in poly-pyrimidine tract binding?
The main genes include PTBP1, PTBP2, PTBP3, U2AF1, U2AF2, SRSF1, SRSF2, HNRNPA1, HNRNPC, RBM17, SRRM4 and others. These genes encode proteins that recognize pyrimidine-rich RNA sequences.
How does poly-pyrimidine tract binding regulate alternative splicing?
Proteins like PTBP1 bind to pyrimidine-rich tracts near 3' splice sites and recruit or block splicing factors, thereby influencing exon inclusion. This regulation is critical during myogenesis and neuronal differentiation.
What diseases are associated with poly-pyrimidine tract binding?
Dysregulation of poly-pyrimidine tract binding is linked to myotonic dystrophy type 1, hematopoietic disorders, cancer and neurological conditions. For example, PTBP1 dysfunction contributes to splicing abnormalities in DM1.
What is the role of PTBP1 in hematopoietic stem cells?
PTBP1 promotes hematopoietic stem cell maintenance and red blood cell development by ensuring sufficient availability of ribosomal constituents.
How can CRISPR be used to study poly-pyrimidine tract binding?
CRISPR knockout, point mutation, knock-in and overexpression models allow researchers to dissect the function of PTBP1 and other poly-pyrimidine tract binding proteins in cell lines and primary cells.
What methods are used to study poly-pyrimidine tract binding?
Common methods include RIP-seq, CLIP-seq, RNA-seq with splicing analysis, EMSA, ITC and CRISPR-based functional genomics.
Is poly-pyrimidine tract binding specific to RNA?
While the GO term defines binding to RNA, PTBP1 has also been shown to interact with a single-stranded DNA motif in a liver-specific enhancer, indicating broader nucleic-acid recognition.
What is the impact of ionic conditions on poly-pyrimidine tract binding?
Monovalent ionic atmosphere modulates the selection of suboptimal RNA sequences by splicing factors' RNA recognition motifs, affecting binding affinity and specificity.
How does poly-pyrimidine tract binding relate to myotonic dystrophy type 1?
In myotonic dystrophy type 1, dysregulation of poly-pyrimidine tract binding proteins contributes to aberrant splicing. Pharmacotherapy can alleviate pathological changes in a human neuronal cell model of DM1.
Conclusion
Poly-pyrimidine tract binding (GO:0008187) is a fundamental molecular function that governs RNA processing, alternative splicing and translation. Its best-characterized mediators, the PTBP family proteins, play essential roles in hematopoiesis, myogenesis and neuronal development. Dysregulation of this activity is implicated in myotonic dystrophy type 1, cancer and other diseases, making it a compelling target for therapeutic intervention. Advances in CRISPR-based models and high-throughput sequencing continue to illuminate the complex regulatory networks controlled by poly-pyrimidine tract binding, offering new opportunities for drug discovery and precision medicine.
References
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- 3. Markopoulos G et al.. 2016. Genomic analysis of mouse VL30 retrotransposons.. Mob DNA 7:10 PMID: 27158269
- 4. Rozza R et al.. 2023. Monovalent Ionic Atmosphere Modulates the Selection of Suboptimal RNA Sequences by Splicing Factors' RNA Recognition Motifs.. J Chem Inf Model 63(10):3086-3093 PMID: 37129986
- 5. Rehn M et al.. 2022. PTBP1 promotes hematopoietic stem cell maintenance and red blood cell development by ensuring sufficient availability of ribosomal constituents.. Cell Rep 39(6):110793 PMID: 35545054
- 6. Capponi S et al.. 2020. Neuronal-specific microexon splicing of TAF1 mRNA is directly regulated by SRRM4/nSR100.. RNA Biol 17(1):62-74 PMID: 31559909
- 7. Fukumura K et al.. 2021. SPF45/RBM17-dependent, but not U2AF-dependent, splicing in a distinct subset of human short introns.. Nat Commun 12(1):4910 PMID: 34389706
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