PT  - JOURNAL ARTICLE
AU  - Swagata Halder
AU  - Ignacio Torrecilla
AU  - Martin D. Burkhalter
AU  - Marta Popovic
AU  - John Fielden
AU  - Bruno Vaz
AU  - Judith Oehler
AU  - Domenic Pilger
AU  - Davor Lessel
AU  - Katherine Wiseman
AU  - Abhay Narayan Singh
AU  - Iolanda Vendrell
AU  - Roman Fischer
AU  - Melanie Philipp
AU  - Kristijan Ramadan
TI  - SPRTN Protease and Checkpoint Kinase 1 Cross-Activation Loop Safeguards DNA Replication
AID  - 10.1101/458026
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 458026
4099  - http://biorxiv.org/content/early/2018/10/31/458026.short
4100  - http://biorxiv.org/content/early/2018/10/31/458026.full
AB  - The SPRTN metalloprotease is essential for DNA-protein crosslink (DPC) repair and DNA replication in vertebrate cells. Cells deficient in SPRTN protease activity exhibit severe DPC-induced replication stress and genome instability, manifesting as premature ageing and liver cancer in humans and mice. Strikingly, SPRTN-deficient cells also show a severe G2/M checkpoint defect and fail to activate a robust checkpoint kinase 1 (CHK1) signalling cascade normally triggered in response to replication stress. Here, we show that SPRTN activates the CHK1 signalling cascade during physiological (steady-state) DNA replication by proteolysis-dependent eviction of CHK1 from chromatin. The N-terminal CHK1 fragments cleaved by SPRTN protease still possess kinase activity and phosphorylate SPRTN. This CHK1-dependent phosphorylation stimulates SPRTN recruitment to chromatin to further promote CHK1 eviction from chromatin, DPC removal and unperturbed DNA replication. Our data suggest that a SPRTN-CHK1 cross-activation loop is essential for steady-state DNA replication and protection from DNA replication stress, a major source of genome instability in diseases that cause premature ageing and cancer. In addition, we disclose a mechanism of CHK1 activation during physiological DNA replication, when long stretches of single stranded (ss) DNA that are induced by genotoxic stress and activate canonical and robust CHK1 signalling are not present.