Centrosome impairment causes DNA replication stress through MLK3/MK2 signaling and R-loop formation

AO_SCPLOWBSTRACTC_SCPLOWCentrosomes function as organizing centers of microtubules and support accurate mitosis in many animal cells. However, it remains to be explored whether and how centrosomes also facilitate the progression through different phases of the cell cycle. Here we show that impairing the composition of centrosomes, by depletion of centrosomal components or by inhibition of polo-like kinase 4 (PLK4), reduces the progression of DNA replication forks. This occurs even when the cell cycle is arrested before damaging the centrosomes, thus excluding mitotic failure as the source of replication stress. Mechanistically, the kinase MLK3 associates with centrosomes. When centrosomes are disintegrated, MLK3 activates the kinases p38 and MK2/MAPKAPK2. Transcription-dependent RNA:DNA hybrids (R-loops) are then causing DNA replication stress. Fibroblasts from patients with microcephalic primordial dwarfism (Seckel syndrome) harbouring defective centrosomes showed replication stress and diminished proliferation, which were each alleviated by inhibition of MK2. Thus, centrosomes not only facilitate mitosis, but their integrity is also supportive in DNA replication. HighlightsO_LICentrosome defects cause replication stress independent of mitosis. C_LIO_LIMLK3, p38 and MK2 (alias MAPKAPK2) are signalling between centrosome defects and DNA replication stress through R-loop formation. C_LIO_LIPatient-derived cells with defective centrosomes display replication stress, whereas inhibition of MK2 restores their DNA replication fork progression and proliferation. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=175 HEIGHT=200 SRC="FIGDIR/small/898684v1_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@41a10corg.highwire.dtl.DTLVardef@b4328dorg.highwire.dtl.DTLVardef@62f373org.highwire.dtl.DTLVardef@5d2c40_HPS_FORMAT_FIGEXP M_FIG C_FIG