| 1. |
- Hannan, Katherine M., et al.
(författare)
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Nuclear stabilization of p53 requires a functional nucleolar surveillance pathway
- 2022
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 41:5
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Tidskriftsartikel (refereegranskat)abstract
- The nucleolar surveillance pathway monitors nucleolar integrity and responds to nucleolar stress by mediating binding of ribosomal proteins to MDM2, resulting in p53 accumulation. Inappropriate pathway activation is implicated in the pathogenesis of ribosomopathies, while drugs selectively activating the pathway are in trials for cancer. Despite this, the molecular mechanism(s) regulating this process are poorly understood. Using genome-wide loss-of-function screens, we demonstrate the ribosome biogenesis axis as the most potent class of genes whose disruption stabilizes p53. Mechanistically, we identify genes critical for regulation of this pathway, including HEATR3. By selectively disabling the nucleolar surveillance pathway, we demonstrate that it is essential for the ability of all nuclear-acting stresses, including DNA damage, to induce p53 accumulation. Our data support a paradigm whereby the nucleolar surveillance pathway is the central integrator of stresses that regulate nuclear p53 abundance, ensuring that ribosome biogenesis is hardwired to cellular proliferative capacity.
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| 2. |
- Quin, Jaclyn, et al.
(författare)
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Inhibition of RNA polymerase I transcription initiation by CX-5461 activates non-canonical ATM/ATR signaling
- 2016
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Ingår i: Oncotarget. - : Impact Journals, LLC. - 1949-2553. ; 7:31, s. 49800-49818
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Tidskriftsartikel (refereegranskat)abstract
- RNA polymerase I (Pol I)-mediated transcription of the ribosomal RNA genes (rDNA) is confined to the nucleolus and is a rate-limiting step for cell growth and proliferation. Inhibition of Pol I by CX-5461 can selectively induce p53-mediated apoptosis of tumour cells in vivo. Currently, CX-5461 is in clinical trial for patients with advanced haematological malignancies (Peter Mac, Melbourne). Here we demonstrate that CX-5461 also induces p53-independent cell cycle checkpoints mediated by ATM/ATR signaling in the absence of DNA damage. Further, our data demonstrate that the combination of drugs targeting ATM/ATR signaling and CX-5461 leads to enhanced therapeutic benefit in treating p53-null tumours in vivo, which are normally refractory to each drug alone. Mechanistically, we show that CX-5461 induces an unusual chromatin structure in which transcriptionally competent relaxed rDNA repeats are devoid of transcribing Pol I leading to activation of ATM signaling within the nucleoli. Thus, we propose that acute inhibition of Pol transcription initiation by CX-5461 induces a novel nucleolar stress response that can be targeted to improve therapeutic efficacy.
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| 3. |
- Sjögren, Sara, et al.
(författare)
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Glucocorticoids improve erythroid progenitor maintenance and dampen Trp53 response in a mouse model of Diamond-Blackfan anaemia.
- 2015
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Ingår i: British Journal of Haematology. - : Wiley. - 0007-1048 .- 1365-2141. ; 171:4, s. 517-529
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Tidskriftsartikel (refereegranskat)abstract
- Diamond-Blackfan anaemia (DBA) is a rare congenital disease causing severe anaemia and progressive bone marrow failure. The majority of patients carry mutations in ribosomal proteins, which leads to depletion of erythroid progenitors in the bone marrow. As many as 40% of all DBA patients receive glucocorticoids to alleviate their anaemia. However, despite their use in DBA treatment for more than half a century, the therapeutic mechanisms of glucocorticoids remain largely unknown. Therefore we sought to study disease specific effects of glucocorticoid treatment using a ribosomal protein s19 (Rps19) deficient mouse model of DBA. This study determines for the first time that a mouse model of DBA can respond to glucocorticoid treatment, similar to DBA patients. Our results demonstrate that glucocorticoid treatment reduces apoptosis, rescues erythroid progenitor depletion and premature differentiation of erythroid cells. Furthermore, glucocorticoids prevent Trp53 activation in Rps19-deficient cells- in a disease-specific manner. Dissecting the therapeutic mechanisms behind glucocorticoid treatment of DBA provides indispensible insight into DBA pathogenesis. Identifying mechanisms important for DBA treatment also enables development of more disease-specific treatments of DBA.
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| 4. |
- Vintermist, Anna, 1980-
(författare)
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Chromatin remodelling of ribosomal genes - be bewitched by B-WICH
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Transcription of the ribosomal genes accounts for the majority of transcription in the cell due to the constant high demand for ribosomes. The number of proteins synthesized correlates with an effective ribosomal biogenesis, which is regulated by cell growth and proliferation. In the work presented in this thesis, we have investigated the ribosomal RNA genes 45S and 5S rRNA, which are transcribed by RNA Pol I and RNA Pol III, respectively.The focus of this work is the chromatin remodelling complex B-WICH, which is composed of WSTF, the ATPase SNF2h and NM1. We have studied in particular its role in ribosomal gene transcription. We showed in Study I that B-WICH is required to set the stage at rRNA gene promoters by remodelling the chromatin into an open, transcriptionally active configuration. This results in the binding of histone acetyl transferases to the genes and subsequent histone acetylation, which is needed for ribosomal gene activation. Study II investigated the role of B-WICH in transcription mediated by RNA polymerase III. We showed that B-WICH is essential to create an accessible chromatin atmosphere at 5S rRNA genes, which is compatible with the results obtained in Study 1. In this case, however, B-WICH operates as a licensing factor for c-Myc and the Myc/Max/Mxd network. Study III confirmed the importance and the function of the B-WICH complex as an activator of ribosomal genes. We demonstrated that B-WICH is important for the remodelling of the rDNA chromatin into an active, competent state in response to extracellular stimuli, and that the association of the B-WICH complex to the rRNA gene promoter is regulated by proliferative and metabolic changes in cells.The work presented in this thesis has confirmed that the B-WICH complex is an important regulator and activator of Pol I and Pol III transcription. We conclude that B-WICH is essential for remodelling the rDNA chromatin into a transcriptionally active state, as required for efficient ribosomal gene transcription.
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