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Role of the WIP1 phosphatase in the nucleolus
Palková, Natálie ; Macůrek, Libor (advisor) ; Sztacho, Martin (referee)
Protein phosphatase 2C delta (known as WIP1) is an important negative regulator of the DNA damage response (DDR) signalling. As a chromatin-bound protein, it dephosphorylates and thus inactivates ATM kinase and the transcription factor p53. Increased expression of WIP1 suppresses the function of the tumour suppressor p53 and contributes to the development of several cancer types, including breast and brain tumours. In recent years, it has been shown that WIP1 can also regulate cellular processes that are not directly linked to DDR, such as ensuring telomere stability. However, alternative functions of the WIP1 protein have not yet been fully understood. In this work, we described a novel role of the WIP1 phosphatase in the nucleolus, the organelle responsible for ribosome biogenesis. We found that WIP1 associates with many nuclear proteins, and using deletion mutants, we identified a nucleolar localisation sequence (NoLS) at the C-terminus of the protein. Using super-resolution microscopy, we detected the localisation of WIP1 phosphatase in the fibrillar centres of the nucleolus. We employed an inducible Cas9 system for generating double-strand breaks in ribosomal DNA and found that WIP1 has an impact on recruitment of DNA repair factors to the nucleolar caps. Analysis based on quantitative...
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