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Molecular mechanisms of genome integrity maintenance under conditions of replication stress
Boleslavská, Barbora ; Dobrovolná, Jana (advisor) ; Hanzlíková, Hana (referee) ; Šebesta, Marek (referee)
Precise and timely duplication of chromosomal DNA is an essential process for all dividing cells. Failure to complete this process can lead to cell death or irreversible changes in genetic information ultimately leading to cell transformation and cancer. The sophisticated multiprotein complex ensuring DNA replication is often slowed down or stalled by numerous obstacles, including DNA lesions and secondary DNA structures, but also by another vitally important cellular process - by ongoing DNA transcription. Head-on transcription-replication collisions (TRCs) associated with the formation of R-loop structures are the major endogenous source of genomic instability. R-loops are three-stranded nucleic acid structures composed of an RNA:DNA hybrid and displaced DNA strand, with a strong potential to halt replication fork progression and to have a genotoxic effect. To ensure complete DNA replication, the eukaryotic cells have developed various mechanisms for removal and overcoming the obstacles to replication fork progression. However, despite the extensive research, the molecular mechanisms underlying the restart of R-loop-stalled replication forks remain unclear. Here, we provide evidence that in human cells the restart of DNA synthesis at the sites of TRCs is a multi-step process involving fork...
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Role of human RECQ5 helicase in the resolution of conflicts between transcription and replication complexes
Fryzelková, Jana ; Dobrovolná, Jana (advisor) ; Vopálenský, Václav (referee)
The progression of replication forks can be slowed down or paused by various external and internal factors during DNA replication. This phenomenon is referred to as replication stress and substantially contributes to genomic instability that is a hallmark of cancer. Transcription complex belongs to the internal replication-interfering factors and represents a barrier for progression of the replication complex. The replication forks are slowed down or paused while passing through the transcriptionally active regions of the genome that can lead to subsequent collapse of stalled forks and formation of DNA double-strand breaks, especially under conditions of increased replication stress. DNA helicase RECQ5 is significantly involved in maintenance of genomic stability during replication stress, but the mechanisms of its action are not clear. In this diploma theses, we have shown that RECQ5 helicase, in collaboration with BRCA1 protein, participates in the resolution of collisions between replication and transcription complexes. BRCA1 protein is a key factor in the homologous recombination process, which is essential for the restart of stalled replication forks. Furthermore, we have shown that RECQ5 helicase is involved in ubiquitination of PCNA protein at stalled replication forks. Key words DNA...
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