The role of MASTL in G₂ DNA damage checkpoint

Abstract

MASTL is the human orthologue of Greatwall kinase (Gwl), which is known to facilitate mitotic entry by inhibiting PP2A via endosulfine (ENSA) and ARPP19. However, the full functions of MASTL in other aspects of cell cycle control in mammalian cell still remained to be deciphered. In this thesis, I study the involvement of MASTL in the G₂ DNA damage checkpoint. After DNA is damaged, cells arrest at G₂ until the damaged DNA is repaired. I found that MASTL did not conserve the mechanism of Greatwall kinase during nuclear exclusion as it did not require the phosphorylation of PLK1 for the binding to 14-3-3, but it conserved the function of Greatwall kinase during checkpoint recovery. MASTL did not take part in checkpoint activation but controlled the timing of checkpoint recovery via PP2A pathway. Depletion of MASTL delayed the recovery while expression of a hyperactive mutant of MASTL promoted the recovery even in absence of PLK1 activity. Also, depletion of MASTL induced premature activation of APC/C after DNA damage and leaded to the subsequent DNA re-replication, which suggested MASTL was required to prevent endo-replication after DNA damage. I also showed that the amount and activity of MASTL have to be monitored precisely as either more or less would impede normal cell growth. These data extended our understanding of MASTL during G₂ DNA damage checkpoint. Based on these findings, I propose that MASTL regulates the G₂ DNA damage checkpoint and is crucial for maintaining the genome stability after DNA damage.

Date of Award	2015
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology