RNASeq was performed from mitotic U2OS osteosarcoma cells that were either unmutated or had been CRISPR/Cas9-modified to carry a homozygous alteration of the genomic region surrounding Serine 2563 of USP9X or that had been transfected with Ctrl or Wt1 siRNA.. The CDK1/CDC14B-USP9X-WT1-IL-8 signalling pathway in mitotic survival

Regulation of mitosis secures cellular integrity and its failure critically contributes to the development, maintenance and treatment resistance of cancer. In yeast, the dual phosphatase Cdc14 controls mitotic progression by antagonizing Cdk1-mediated protein phosphorylation. By contrast, specific mitotic functions of the mammalian Cdc14 orthologue CDC14B have remained largely elusive. Here, we find that CDC14B antagonizes CDK1-mediated activating mitotic phosphorylation of the deubiquitinase USP9X at Serine residue 2563, which we show to be essential for USP9X to mediate mitotic survival. Starting from an unbiased proteome-wide screening approach, we specify Wilms’ tumor protein 1 (WT1) as the relevant substrate that becomes deubiquitylated and stabilized by serine 2563-phosphorylated USP9X in mitosis. We further demonstrate that WT1 functions as a mitotic transcription factor and specify CXCL8/IL-8 as a target gene of WT1 that conveys mitotic survival. Together, we describe a ubiquitin dependent signaling pathway that directs a mitosis-specific transcription program to regulate mitotic survival.