PIP4K2B is mechanoresponsive and controls heterochromatin-driven nuclear softening through UHRF1

Phosphatidylinositol-5-phosphate (PtdIns5P)-4-kinases (PIP4Ks) are stress-regulated phosphoinositide kinases able to phosphorylate PtdIns5P to PtdIns(4,5)P2. In cancer patients their expression is typically associated with bad prognosis. Among the three PIP4K isoforms expressed in mammalian cells, PIP4K2B is the one with more prominent nuclear localization. Here, we unveil the role for PIP4K2B as mechanosensor. PIP4K2B protein level, indeed, strongly decreases in cells growing on soft substrates. Its direct silencing or pharmacological inhibition, mimicking cell response to soft, triggers a concomitant reduction of the epigenetic regulator UHRF1 and induces changes in nuclear polarity, nuclear envelope tension and chromatin compaction. This substantial rewiring of the nucleus mechanical state drives YAP cytoplasmic retention and impairment of its activity as transcriptional regulator, finally leading to defects in cell spreading and motility. Since YAP signalling is essential for initiation and growth of human malignancies, our data suggest that potential therapeutic approaches targeting PIP4K2B could be beneficial in the control of the altered mechanical properties of cancer cells. RNA-seq, 3 replicates per condition , 3 conditions (sh_Ctrl, sh_2B, Soft), 1 cell line. Data is available under CC BY 4.0 license. This project was supported by Italian Association for Cancer Research (AIRC) Investigator Grant (Paolo Maiuri, #24976) and individual fellow- ship (Fabrizio A. Pennacchio, #23966). Alessandro Poli's work was founded by Fondazione Umberto Veronesi Post-doctoral fellowships (#000359) and Short-EMBO Fellowship (#8386). Polish National Science Centre grant founded Paulina Nastaly (#2020/39/D/NZ3/00882).