Linear ubiquitination of p31comet by HOIP couples cytokine response with mitotic regulation.

Background: Inflammation and genomic instability are among the hallmarks of human cancer. Proinflammatory cytokines induce DNA damage through the accumulation of reactive oxygen and nitrogen species (RONS), which often leads to base alternations. The link between proinflammatory cytokines and chromosomal instability remains largely elusive.

Results: Here, we report that the mitotic checkpoint protein p31^comet (MAD2L1BP) is modified by linear ubiquitination via the E3 ubiquitin ligase HOIP after cytokine stimulation. HOIP-mediated polyubiquitination of p31^comet occurs on its C-terminal lysine residues. Ubiquitinated p31^comet displays reduced binding to PLK1, which phosphorylates and inactivates p31^comet. Thus HOIP positively  regulates p31^comet function. Consistent with this notion, HOIP-deficient cells exhibit prolonged mitotic duration similar to p31^comet knockout. Mitotic defects are also more prevalent in cells without HOIP or p31^comet. Moreover, compared with the cells expressing wild-type p31^comet, cells expressing a ubiquitination-deficient p31^comet mutant take more time to complete the M phase.

Conclusions: Our results together uncover a mechanistic link between the proinflammatory cytokines and the mitotic checkpoint pathways. This molecular switch could be explored as a potential therapeutic target in inflammation-driving or p31^comet overexpressed cancer types.