 U1SNRNP is a key regulator of mRNA biogenesis through its roles in splicing, and transcription, and 3N processing. Here the authors show a tumor suppressor-like function of U1SNRNP using in vitro cell migration, invasion assays, and transcriptome profiling. This article was authored by Jung Minit-O, Christopher C. Venters, Chow D. I., and others.