Budding uninhibited by benzimidazoles 1 (BUB1) is a nuclear serine/threonine protein kinase that ensures proper chromosome segregation before mitosis. We report that BUB1 plays an unexpected cytoplasmic role in restraining DNA damage-induced accumulation of cytoplasmic dsRNA and the ensuing immune response. Tumors deficient in BUB1 were sensitive to radiotherapy in a CD8 T cell-dependent manner. We found increased immune cell infiltration accompanied by elevated type I interferon production from irradiated BUB1-deficient cells caused by enhanced cytoplasmic dsRNA accumulation and activation of the MDA5/MAVS dsRNA-sensing pathway. Mechanistically, we found that after radiation exposure, BUB1 underwent nucleus-to-cytoplasm migration, where it bound and phosphorylated the poly(A)-binding protein PABPC1, which was degraded together with its associated messenger RNAs stored in the stress granules, thereby preventing dsRNA accumulation and activation of the innate immune response.
Hu et al. (Fri,) studied this question.