Integrative CRISPR Screening and RNA Analyses Discover an Essential Role for PUF60 Interactions with 3' Splice Sites in Cancer Progression.

RNA-binding proteins (RBPs) are important regulators of post-transcriptional gene expression. Understanding which and how RBPs promote cancer progression is crucial for cancers that lack effective targeted therapies, such as triple negative breast cancer (TNBC). Here, we employed both in vitro and in vivo pooled CRISPR/Cas9 screening to identify 50 RBP candidates essential for TNBC cell survival. Integrated eCLIP and RNA-sequencing analysis identified that poly(U)-binding splicing factor 60 (PUF60) drives exon inclusion within proliferation-associated transcripts that, when mis-spliced, induce cell cycle arrest and DNA damage. Furthermore, disrupting PUF60 interactions with 3' splice sites via a substitution in its RNA-binding domain caused widespread exon skipping, leading to downregulation of proliferation-associated mRNAs and inducing apoptosis in TNBC cells. Knockdown of PUF60 or disruption of PUF60-RNA interactions inhibited TNBC cell proliferation and shrunk tumor xenografts in multiple models. Together, these findings reveal the molecular mechanism by which PUF60 supports cancer progression.