Re-analysis of CLAP data affirms PRC2 as an RNA binding protein.

Using CLAP methodology, Guo et al. recently concluded that PRC2 is not an RNA binding protein (RBP). They suggest that prior findings were CLIP artifacts and argue against RNA's direct role in PRC2 regulation. Here, we re-analyze their raw datasets and reach contrary conclusions. Through an independent computational pipeline, we observe significant PRC2 enrichment throughout the transcriptome, including XIST. Applying the authors' published computational pipeline also reaffirms PRC2 as an RBP. Detailed investigation of the authors' pipeline reveals several unconventional practices. First, Guo et al. retained reads from foreign species and other unmappable reads to obtain a normalization factor. Second, they selectively removed read duplicates from the mappable fraction, while retaining them in the unmappable fraction. Finally, the authors applied an arbitrary cutoff for enrichment values in XIST. Their pipeline thereby inflated PRC2's background reads and suppressed mappable signals, creating the impression that PRC2 is not a robust RBP.