Aurora-B Mediated ATM Serine 1403 Phosphorylation Is Required for Mitotic ATM Activation and the Spindle Checkpoint

Abstract

Summary The ATM kinase plays a critical role in the maintenance of genetic stability. ATM is activated in response to DNA damage and is essential for cell cycle checkpoints. Here, we report that ATM is activated in mitosis in the absence of DNA damage. We demonstrate that mitotic ATM activation is dependent on the Aurora-B kinase and that Aurora-B phosphorylates ATM on serine 1403. This phosphorylation event is required for mitotic ATM activation. Further, we show that loss of ATM function results in shortened mitotic timing and a defective spindle checkpoint, and that abrogation of ATM Ser1403 phosphorylation leads to this spindle checkpoint defect. We also demonstrate that mitotically-activated ATM phosphorylates Bub1, a critical kinetochore protein, on Ser314. ATM-mediated Bub1 Ser314 phosphorylation is required for Bub1 activity and is essential for the activation of the spindle checkpoint. Collectively, our data highlight mechanisms of a critical function of ATM in mitosis.

Interplay between the DNA Damage Proteins MDC1 and ATM in the Regulation of the Spindle Assembly Checkpoint

“…In addition, ATM is phosphorylated and activated by Aurora-B. ATM then phosphorylates Bub1 (27); however, it was not demonstrated how this phosphorylation event contributes to SAC activation. Depletion of Aurora-B or Bub1 results in impairment in the localization of BubR1 and Mad2 at kinetochores (50 -52).…”

“…Furthermore, ATM is phosphorylated during the SAC by Aurora-B and then phosphorylates Bub1, which is required for the localization of the sub-complex BubR1-Bub3 at mitotic kinetochores ( Fig. 8) (27). These two functions of ATM are probably not connected.…”

“…Furthermore, ATM is phosphorylated on serine 1403 during mitosis by the Aurora-B kinase. This mitotically activated ATM phosphorylates the SAC protein Bub1 (27). Loss of ATM function results in shortened mitotic timing and a defective SAC (27).…”

“…This mitotically activated ATM phosphorylates the SAC protein Bub1 (27). Loss of ATM function results in shortened mitotic timing and a defective SAC (27). Finally, MDC1 is hyperphosphorylated in cells arrested in mitosis (28 -30).…”

Degradation of Human RAP80 is Cell Cycle Regulated by Cdc20 and Cdh1 Ubiquitin Ligases

“…6G, no differences in the level of g-H2AX were detected throughout the cell cycle. Because nocodazole has been reported to either cause DNA damage (19) or not to cause DNA damage (20), immunofluorescence microscopy staining for gH2AX foci (an index of DNA DSBs) was carried HA-Cdh1 : Figure 4. (Continued ) F and G, Cdc20 and Cdh1-mediated RAP80 ubiquitination is dependent on the D box1.…”