| dc.contributor.advisor | Dobbelstein, Matthias Prof. Dr. | |
| dc.contributor.author | Manzini, Valentina | |
| dc.date.accessioned | 2022-11-04T10:53:55Z | |
| dc.date.available | 2022-11-12T00:50:09Z | |
| dc.date.issued | 2022-11-04 | |
| dc.identifier.uri | http://resolver.sub.uni-goettingen.de/purl?ediss-11858/14323 | |
| dc.identifier.uri | http://dx.doi.org/10.53846/goediss-9537 | |
| dc.language.iso | eng | de |
| dc.rights.uri | http://creativecommons.org/licenses/by/4.0/ | |
| dc.subject.ddc | 570 | de |
| dc.title | Non-canonical functions of the MDM2 oncoprotein | de |
| dc.type | doctoralThesis | de |
| dc.contributor.referee | Papantonis, Argyris Prof. Dr. | |
| dc.date.examination | 2022-03-08 | de |
| dc.description.abstracteng | The tumour suppressor gene TP53 is mutated in ~50% of human cancers. The p53 protein is a transcription factor which is induced by several cellular stresses, such as ribosomal stress and DNA damage. Expression of its target genes leads to cell cycle arrest, apoptosis, or senescence. MDM2 is one of these target genes and acts as a negative regulator by binding to p53, leading to its proteasomal degradation and inhibition. MDM2 and p53 are thus linked by a negative feedback loop which provides cells with an additional layer of regulation. In recent years, several non-canonical functions of the E3 ubiquitin ligase MDM2 have been uncovered which do not involve the negative regulation of p53. In this thesis we investigated two of these non-canonical roles, in the context of ribosome biogenesis and DNA replication.
Firstly, we employed the proteolysis targeting chimera (PROTAC) strategy to deplete MDM2 in proliferating cells, in the presence of p53 activation. We found that MDM2 accumulation inhibits RNA Polymerase III activity and reduces the levels of nascent 5S rRNA, an essential component of the ribosomes, through interaction with the ribosomal proteins RPL5 and RPL11. Prolonged p53 activation and MDM2 accumulation, via treatment with the cis-imidazoline analog Nutlin-3, led to disrupted ribosome biogenesis and diminished RNA Pol I activity, independent of external stresses.
Secondly, we showed that MDM2 represses fork reversal, a protective mechanism that reverses DNA replication forks in the presence of DNA damage. MDM2 accumulation also increased the progression of of DNA replication forks, and depletion of either the helicase RECQ1, or the primase-polymerase PRIMPOL, reversed this effect. Poly- (ADP-ribose) polymerase 1 (PARP1) was previously shown to prevent premature restart of reversed forks through inhibition of RECQ1. Here, we identified MDM2 as a novel interaction partner of PARP1 which mediates its proteasomal degradation and inhibition.
Taken together, MDM2 performs at least two additional functions, on top of antagonizing p53. It dampens the synthesis of an entire class of RNAs, i.e. Polymerase III transcripts, and it prevents a protective mechanism for DNA replication forks. We speculate that these non-canonical functions of MDM2 might contribute to cell death in the context of p53 activation. | de |
| dc.contributor.coReferee | Bohnsack, Markus Prof. Dr. | |
| dc.subject.eng | Molecular Biology | de |
| dc.subject.eng | Cancer | de |
| dc.subject.eng | p53 | de |
| dc.subject.eng | MDM2 | de |
| dc.subject.eng | DNA replication | de |
| dc.subject.eng | Ribosome Biogenesis | de |
| dc.subject.eng | Molecular Oncology | de |
| dc.identifier.urn | urn:nbn:de:gbv:7-ediss-14323-1 | |
| dc.affiliation.institute | Göttinger Graduiertenschule für Neurowissenschaften, Biophysik und molekulare Biowissenschaften (GGNB) | de |
| dc.subject.gokfull | Biologie (PPN619462639) | de |
| dc.description.embargoed | 2022-11-12 | de |
| dc.identifier.ppn | 1820789810 | |
| dc.notes.confirmationsent | Confirmation sent 2022-11-04T11:15:01 | de |