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Abstract RNA-binding proteins (RBPs) are key regulators of gene expression. RBP dysregulation is reported to play essential roles in tumorigenesis. However, the role of RBPs in urothelial carcinoma of the bladder (UCB) is only starting to be unveiled. Here, we comprehensively assessed the mRNA expression landscape of 104 RBPs from two independent UCB cohorts, Sun Yat-sen University Cancer Center (SYSUCC) and The Cancer Genome Atlas (TCGA). Fragile X-related gene 1 (FXR1) was identified as a novel cancer driver gene in UCB. FXR1 overexpression was found to be related to the poor survival rate in the SYSUCC and TCGA cohorts. Functionally, FXR1 promotes UCB proliferation and tumorigenesis. Mechanistically, FXR1 serves as a platform to recruit CFIm25 and CFIm68, forming a novel 3′ processing machinery that functions in sequence-specific poly(A) site recognition. FXR1 affects the 3′ processing of Tumor necrosis factor receptor-associated factor 1 (TRAF1) mRNA, which leads to nuclear stabilization. The novel regulatory relationship between FXR1 and TRAF1 can enhance cell proliferation and suppress apoptosis. Our data collectively highlight the novel regulatory role of FXR1 in TRAF1 3′ processing as an important determinant of UCB oncogenesis. Our study provides new insight into RBP function and provides a potential therapeutic target for UCB.