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The role of CRL4 ubiquitin ligase complex in homeostasis and regeneration of gastro intestinal tract
Daněk, Veronika ; Procházka, Jan (advisor) ; Janečková, Lucie (referee) ; Čermák, Lukáš (referee)
Ubiquitination represents a central regulatory mechanism for protein function utilization. Dysfunction of ubiquitin ligases is associated with the development of various pathological conditions. However, the full complexity of the ubiquitinating network in tissue homeostasis and carcinogenesis remains to be elucidated, limiting its potential as a therapeutic target. In my PhD project, I aimed to reveal the role of E3 ubiquitin ligases, particularly CUL4A, in the alteration of regulatory pathways that result in gastrointestinal (GIT) homeostasis disorders and tumor expansion. By using a novel semantic biclustering technique, we performed expression profiling of the E3 ubiquitin ligases and uncovered the potentially redundant features of GIT-specific ubiquitin ligases based on their tissue-specific expression and ontological relationships. Testing the identified compensatory network on the mouse model showed that genes from the same ontology group simultaneously altered their expression pattern after induced epithelial damage, exposing their complementary role during tissue regeneration. Next, I focused on CUL4A, a scaffold of the Cullin4-RING E3 ubiquitin ligase complex (CRL4). We described that CUL4A is expressed by populations of secretory cells in the small intestine and colon. CUL4A deficiency...
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New molecular mechanisms involved in cell cycle control
Aquino, Cecilia ; Macůrek, Libor (advisor) ; Anger, Martin (referee) ; Braun, Marcus (referee)
Cecilia Aquino Perez, M. Sc. Doctoral thesis abstract In this doctoral, thesis we aimed to find and study novel mechanisms regulating cell cycle phase transitions in non-stressed conditions and in context of the cell response to various types of stress. First, we focused on studying Polo-like kinase 3 that has previously been implicated in activation of the cell cycle checkpoint after DNA damage. For this, we employed CRISPR/Cas9- mediated gene editing to knock-out PLK3 in RPE cells while in parallel performing RNA interference assays and submitting the cells to different types of stress. The main observation was that in both systems PLK3 was disposable for response to DNA damage, hypoxia and osmotic stress. Through mass spectrometry analysis of purified EGFP-PLK3 we identified PP6 and its regulatory subunits PPP6R1 and PPP6R3 as novel PLK3 interactors. We observed that PLK3 is phosphorylated in its conserved residue Thr-219 and that PP6 depletion boosted PLK3 phosphorylation status but did not affect its kinase activity. The possible regulation of PLK3 trough PP6 is interesting and its biological relevance will be addressed by future research. Next, we performed a transcriptomic analysis in human RPE-FUCCI cells aiming to identify new regulators of the cell cycle. We selected Family with sequence...
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