Improved binding site assignment by high-resolution mapping of RNA-protein interactions using iCLIP

Area of Science:

• Molecular Biology
• Genomics
• Biochemistry

Background:

• Individual-nucleotide resolution crosslinking and immunoprecipitation (iCLIP) is a technique used to map RNA-binding protein (RBP) interactions on RNA.
• The method relies on UV-induced crosslinking, followed by reverse transcription and high-throughput sequencing, with fragment start sites ideally pinpointing direct RBP-RNA interactions.
• However, observed fragment start sites in iCLIP data can exhibit broader distributions than expected, potentially obscuring precise binding locations.

Purpose of the Study:

• To investigate the phenomenon of broader fragment start site distributions in iCLIP data for several RBPs.
• To determine if fragment length influences the observed distribution of crosslinking sites.
• To develop a computational tool to correct for these shifts and improve the accuracy of RBP binding site mapping.

Main Methods:

• Application of iCLIP to study multiple RNA-binding proteins, including eIF4A3, PTB, SRSF3, SRSF4, and hnRNP L.
• Analysis of iCLIP fragment start site distributions in relation to fragment length.
• Development and implementation of a novel analysis tool to identify and correct for fragment length-dependent shifts in crosslinking sites.

Main Results:

• For several tested RBPs, iCLIP fragment start sites showed a broader distribution than anticipated.
• This broadening was dependent on fragment length and could result in shifts upstream of the actual RBP binding site.
• The developed analysis tool successfully identified these shifts and demonstrated an improvement in the precise localization of RBP binding sites.

Conclusions:

• Standard iCLIP analysis may mislocalize RBP binding sites due to fragment length-dependent effects.
• The newly developed analysis tool offers a significant improvement for accurate RBP binding site determination using iCLIP data.
• This advancement enhances the utility of iCLIP for understanding RBP-RNA interactions in molecular biology and genomics research.