What is CLIP-seq?

Scientists often want to know how proteins interact with RNA inside cells. These interactions are important because they help control how genes work and how cells behave. CLIP-seq, which stands for "Crosslinking and Immunoprecipitation followed by Sequencing," is a method that helps researchers find out exactly where proteins bind to RNA.

In CLIP-seq, researchers shine ultraviolet (UV) light onto cells. This makes proteins and RNA stick together where they touch. Next, they use special antibodies to pull out these protein-RNA pairs from the rest of the cell. After that, they break the RNA into small pieces and turn it into DNA. Finally, they sequence this DNA to learn where the proteins were bound on the RNA.

Compared to a simpler method called RIP-seq (RNA Immunoprecipitation sequencing), CLIP-seq has two big advantages:

• Higher specificity: UV light ensures that only proteins directly touching the RNA get linked, which reduces false positives.
• Better resolution: CLIP-seq shows exactly which part of the RNA the protein was binding to, sometimes down to a few nucleotides.

CLIP-seq Technologies Packages

Classic CLIP-seq (HITS-CLIP)

Classic CLIP-seq, sometimes called HITS-CLIP, uses UV light to crosslink proteins and RNA directly inside cells. Scientists then use antibodies to pull out these protein-RNA pairs. Next, the RNA is converted into DNA and sequenced. This method provides a broad, genome-wide map of where proteins bind to RNA.

iCLIP-seq (Individual-nucleotide Resolution CLIP)

iCLIP-seq is designed to map protein–RNA interactions with single-nucleotide precision. During the reverse transcription step, iCLIP captures where the enzyme stalls due to crosslinked proteins, creating precise "cut-off" points.

This technology is particularly useful for studying:

• Splicing regulation
• RNA maturation
• Non-coding RNA function

iCLIP-seq helps researchers identify exact protein binding positions on RNA, making it ideal for high-resolution studies.

miCLIP-seq (Methylation Individual-nucleotide Resolution CLIP)

miCLIP-seq is a specialized version of iCLIP used to study RNA modifications, particularly m6A methylation.

By combining UV crosslinking with specific antibodies against methylated bases, miCLIP-seq allows researchers to detect:

• Single-nucleotide resolution methylation sites
• Binding sites of "reader" proteins that recognize RNA modifications

This technique is crucial for understanding epitranscriptomic regulation and how chemical changes to RNA affect gene expression and cell function.

eCLIP-seq (Enhanced CLIP-seq)

eCLIP-seq improves on traditional CLIP methods by adding size-matched input controls to better distinguish real binding events from background noise.

Benefits of eCLIP-seq include:

• Higher signal-to-noise ratio
• Improved reproducibility
• Greater confidence in identifying true protein-RNA interactions

eCLIP-seq has become a popular method for large-scale projects, such as ENCODE, where precise and reproducible data is essential.

PAR-CLIP-seq

PAR-CLIP-seq involves feeding cells molecules called photoreactive ribonucleoside analogs, like 4-thiouridine (4SU). These get incorporated into newly transcribed RNA. When UV light hits the cells, it promotes stronger crosslinking between the RNA and bound proteins.

A unique feature of PAR-CLIP is its ability to pinpoint exact binding sites at the nucleotide level, often detected through characteristic T-to-C conversions in the sequence data.

Comparison of ATAC-seq, ChIP-seq, CUT&Tag, RIP-seq, and CLIP-seq

Researchers often wonder which sequencing technology best fits their study. N2 Jenomics Lab Pvt. Ltd. offers all these methods to help you explore gene regulation from different angles. The table below makes it easy to compare these powerful tools:

Each method provides unique insights. You can choose a single technique or combine several for deeper analysis.

"At N2 Jenomics Lab Pvt. Ltd. , we are committed to staying one step ahead through constant innovation. We have built deep expertise in epigenomics, not only focusing on core technologies like methylation analysis, ATAC-seq, ChIP-seq, and RIP-seq, but also embracing cutting-edge methods such as CLIP-seq and CUT&Tag. Our goal is to help clients solve even the most complex challenges in epigenetic research."

CLIP-seq Experimental Workflow

CLIP-seq Bioinformatics

Core Data Processing

Once we receive the sequencing data, we start by cleaning it up. This involves:

• Quality control: Checking for errors or low-quality reads that might cause problems later.
• Adapter trimming: Removing leftover pieces of DNA used during library preparation.
• Mapping reads: Aligning each RNA fragment to the right spot on the genome.

Advanced Analysis and Functional Interpretation

• Peak calling: Identifying regions where many RNA fragments pile up, signaling a protein-binding site.
• Motif discovery: Searching for short RNA sequences that proteins prefer to bind.
• Positional analysis: Examining where binding sites occur, like near the start or end of genes (TSS, TTS, start/stop codons).
• GO and KEGG pathway analysis: Linking bound genes to known biological functions and pathways.
• Differential analysis: Comparing samples to see how binding changes under different conditions.
• CIMS analysis: Detecting tiny changes in RNA caused by the crosslinking process, helping pinpoint binding sites.

We also create clear graphs and visualizations to help researchers see and interpret their results.

Multi-Omics Integration

Modern research often involves multiple types of data. N2 Jenomics Lab Pvt. Ltd. helps researchers combine CLIP-seq with:

• ChIP-seq: Studying protein-DNA interactions.
• ATAC-seq: Finding open regions of DNA.
• RNA-seq: Measuring gene expression levels.

Advantages of Our CLIP-seq Services

Extensive Experience Across Diverse Species and Sample Types

Our team has handled CLIP-seq projects for a wide variety of organisms, including:

• Humans
• Mice, rats, and other animals
• Plants such as rice, wheat, and tomato
• Microorganisms like bacteria and fungi

High Success Rates

CLIP-seq experiments can be complex. But at N2 Jenomics Lab Pvt. Ltd. , our success rates exceed 95%, thanks to:

• Optimized lab protocols
• Careful experimental design
• Rigorous quality control

Proprietary Peak-Calling Algorithms

We've developed our own algorithms for peak calling, the critical step of identifying where proteins bind to RNA. Our proprietary methods:

• Reduce background noise
• Improve detection of real binding events
• Deliver clearer, more reliable results

Customized Multi-Omics Analyses

Every research question is different. That's why we offer customized data analysis and multi-omics integration, allowing you to:

• Connect CLIP-seq data with ChIP-seq, ATAC-seq, or RNA-seq results
• Explore complex regulatory networks
• Gain a deeper understanding of gene expression and regulation

Strict Antibody Quality Validation

Antibodies are the key tools in CLIP-seq. We:

• Test every antibody for specificity and efficiency
• Provide validation data to ensure confidence in results
• Help clients choose the right reagents for their targets

Quick Turnaround Times and High-Quality Deliverables

We know that time matters in research. N2 Jenomics Lab Pvt. Ltd. offers:

• Fast project turnaround
• Detailed, publication-ready reports
• Clean, well-organized data files for easy downstream analysis

Strong Publication Record

Our scientists have contributed to studies published in top-tier journals like Nature, Cell, and Molecular Cell. We bring that same level of scientific rigor to every client project.

Applications of CLIP-seq

1

Understanding RNA-Binding Proteins (RBPs)

• How genes are turned on or off
• How cells respond to stress
• How different cell types develop unique identities

2

Studying Alternative Splicing

• Discover new RNA variants
• Understand how splicing errors contribute to disease
• Identify new targets for drug development

3

Exploring Non-Coding RNAs (ncRNAs)

• Discover how RBPs interact with non-coding RNAs
• Reveal new functions for these mysterious molecules
• Identify potential biomarkers for research applications

4

Identifying miRNA Targets

• High-confidence identification of miRNA target sites
• Insights into how miRNAs regulate specific biological pathways

5

Supporting Drug Target Discovery

• Identify RBPs or RNA regions involved in disease-related pathways
• Study how experimental drugs affect RNA-protein interactions
• Find potential biomarkers for drug development

Sample Requirements

Our HLA typing service provides high-resolution data tailored to support diverse research applications. Here's a quick overview of how to interpret the results.

Demo Results

Precise CLIP-seq FAQs

1. What is CLIP-seq and why is it important?

CLIP-seq combines UV crosslinking, immunoprecipitation, and sequencing to map RNA-protein interactions at a transcriptome-wide scale. This provides precise insights into how RNA-binding proteins regulate gene expression post-transcriptionally .

2. How does CLIP-seq differ from RIP-seq?

RIP‑seq pulls down RNA-protein complexes without crosslinking, leading to more background noise and less precise binding site identification. CLIP-seq uses UV crosslinking to capture direct, in vivo interactions, offering higher specificity and single-nucleotide resolution .

3. What resolution can I expect with CLIP-seq variants like iCLIP or PAR-CLIP?

iCLIP captures truncated cDNAs at crosslink sites, enabling individual-nucleotide resolution and precise protein–RNA binding location.

PAR-CLIP, using photoactivatable nucleosides, introduces characteristic mutations (e.g., T-to-C) that help pinpoint binding sites down to specific nucleotides.

4. How is CLIP-seq data processed and analyzed?

Typical analysis includes:

• Adapter removal, molecular barcodes/barcode trimming
• Mapping reads to a reference genomePeak calling to identify binding sites
• Motif discovery and binding site quality checks
• Pipelines like CLIPipe, PureCLIP, and PEAKachu are commonly used for robust analysis workflows.

5. What types of samples and input quantities are needed?

CLIP-seq typically requires 10–30 million cells or 10–500 mg of tissue, depending on the specific method. Variants like GoldCLIP or irCLIP may accept lower inputs, but overall yield and protein abundance are critical considerations. It is best to consult CD Genomics for sample-specific advice.

6. Can CLIP-seq detect RNA modifications like m6A?

Yes. Variant methods such as miCLIP-seq combine CLIP with antibodies targeting modified RNA bases—especially m6A—to map modified nucleotides at single-nucleotide resolution, helping understand epitranscriptomic regulation.

7. How do I validate antibody specificity in CLIP-seq?

High-quality CLIP-seq relies on validated antibodies. Researchers should ensure their antibodies are specific and work well in immunoprecipitation. Tools like Western blot and IP-qPCR are recommended before proceeding to CLIP-seq.

8. What controls are necessary in CLIP-seq experiments?

Controls such as input samples, size-matched input (SMI) for eCLIP, and IgG or no-antibody controls are vital. These controls help distinguish true binding events from background noise.

9. How do I choose between CLIP variant methods?

• Use iCLIP for nucleotide-precise mapping
• Choose PAR-CLIP for strong signal via photoreactive nucleosides
• Consider GoldCLIP or irCLIP for safer protocols without radioactivity
• Use eCLIP for standardized input controls and robust reproducibility

Precise CLIP-seq Case Studies

Case Study: PRRC2B-mRNA Interactions Mapped by PAR-CLIP-seq

Journal: Nucleic Acids Research

Impact Factor: 19.160 (2022)

Published: 2023

PMC10287950

Background

RNA-binding proteins (RBPs) play crucial roles in regulating gene expression post-transcriptionally, influencing processes such as splicing, translation, and RNA stability. However, the functions and binding patterns of many RBPs remain poorly characterized. This study focused on PRRC2B, a poorly understood RBP suspected of influencing cell cycle progression and cancer-related pathways. The researchers aimed to identify genome-wide RNA binding sites of PRRC2B and explore its functional role in translational regulation.

Materials & Methods

Sample Preparation

• Cell Line: HEK293T
• Incorporation of photoreactive ribonucleoside analog 4-thiouridine (4SU)
• UV crosslinking at 365 nm
• Immunoprecipitation & Sequencing
• Immunoprecipitation of PRRC2B-RNA complexes
• Library preparation and PAR-CLIP sequencing

Data Analysis

• Mapping reads to the human genome
• Identification of crosslink-induced mutation sites (CIMS)
• Motif analysis
• Ribosome profilingfor translation efficiency
• Functional assays including PRRC2B knockdown and rescue experiments

Results

1. PRRC2B Binding Site Identification
   • Genome-wide binding sites of PRRC2B were mapped with single-nucleotide resolution.
   • PRRC2B preferentially bound near the start codon regions of a subset of mRNAs.
   • Enriched motifs included CU- or GA-rich sequences in 5' UTRs and coding sequences.
2. Functional Consequences of PRRC2B Binding
   • PRRC2B knockdown led to:
   • Reduced translation of target mRNAs
   • Decreased levels of cell-cycle regulatory proteins, including CCND2
   • G1/S phase arrest and reduced cell proliferation
3. Antisense oligonucleotides disrupting PRRC2B binding at specific motifs reduced translation of CCND2.
   • Mechanistic Insights
   • PRRC2B interacts with translation initiation factors eIF3 and eIF4G2 in an RNA-independent manner.
   • Mutations disrupting PRRC2B's interactions with initiation factors failed to rescue translation defects caused by PRRC2B knockdown.

Proline-rich coiled-coil 2B (PRRC2B) binds to CU- or GA-rich motifs on specific mRNAs, facilitates their translation through interacting with eIF4G2 and eIF3, and promotes cell cycle progression and cell proliferation.

Conclusion

This study provides the first comprehensive, high-resolution map of PRRC2B-RNA interactions in human cells, demonstrating that PRRC2B binds near translation start sites and enhances translation of key cell-cycle regulators. Disruption of these interactions impairs cell cycle progression, suggesting a novel mechanism for translational control. These insights highlight PRRC2B as a potential regulatory node in cancer biology and cell proliferation pathways.

Reference

1. Jiang, F., Hedaya, O. M., Khor, E. S., et al. (2023). RNA binding protein PRRC2B mediates translation of specific mRNAs and regulates cell cycle progression. Nucleic Acids Research. PMC10287950