PUS1 Drives Renal Cancer Progression by Preventing Formation of Endogenous Double-stranded RNAs.

Pseudouridine (Ψ) modification is a prevalent epitranscriptomic mark with critical roles in carcinogenesis; however, the function of its catalytic "writer" enzyme, pseudouridine synthase 1 (PUS1), in renal cell carcinoma (RCC) remains elusive. Our analysis revealed that PUS1 mRNA is upregulated in RCC and is associated with an unfavorable prognosis. Strikingly, this transcriptional upregulation results in a concomitant and exclusive increase in the protein abundance of PUS1 isoform 2. Mechanistically, although PUS1 markedly enhances global mRNA translation, this effect is not directly mediated via Ψ modification of either mRNA or tRNA. Instead, PUS1 regulates pre-mRNA splicing, and its deficiency induces elevated intron retention. This, in turn, culminates in the formation of double-stranded RNA (dsRNA), which subsequently activates the innate antiviral immune response and inhibits global translation. Furthermore, depletion of PUS1 in tumor cells significantly sensitizes RCC to immune checkpoint blockade therapy. Collectively, our findings demonstrate that PUS1 shields tumor cells from endogenous dsRNA accumulation and the consequent detrimental innate immune activation, thereby unveiling a novel and promising therapeutic strategy for RCC.