Checkpoint kinase 1-induced phosphorylation of O-linked {beta}-N-acetylglucosamine transferase regulates the intermediate filament network during cytokinesis [Cell Biology] (Journal of Biological Chemistry)

Checkpoint kinase 1 (Chk1) is a kinase instrumental for orchestrating DNA replication, DNA damage checkpoints, the spindle assembly checkpoint, and cytokinesis. Despite Chk1`s pivotal role in multiple cellular processes, many of its substrates remain elusive. Here, we identified O-linked ?-N-acetylglucosamine (O-GlcNAc)-transferase (OGT) as one of Chk1`s substrates. We found that Chk1 interacts with and phosphorylates OGT at Ser-20, which not only stabilizes OGT, but also is required for cytokinesis. Phospho-specific antibodies of OGT-pSer-20 exhibited specific signals at the midbody of the cell, consistent with midbody localization of OGT as reported previously. Moreover, phospho-deficient OGT (S20A) cells attenuated cellular O-GlcNAcylation levels and also reduced phosphorylation of Ser-71 in the cytoskeletal protein vimentin, a modification critical for severing vimentin filament during cytokinesis. Consequently, elongated vimentin bridges were observed in cells depleted of OGT via an siOGT-based approach. Lastly, expression of plasmids resistant to siOGT efficiently rescued the vimentin bridge phenotype, but the OGT-S20A rescue plasmids did not. Our results suggest a Chk1-OGT-vimentin pathway that regulates the intermediate filament network during cytokinesis.