To this date, cancer is still one of the most common causes of death. In most cases cancer starts with a mutation or a deletion in a gene. This mutation/deletion leads to increased genome instability, enhanced cell growth and consequently to tumor formation. Obviously, many biological processes are altered in such cancer cells. To understand the causes and consequences of tumor formation the complete understanding of healthy cells or the "normal" biological state is essential.
It has been shown that DNA can form in addition to a double helix alternative structures, which have a great impact on various biological processes. In the last years I have focused on understanding the biological impact of DNA secondary structures on genome stability. My lab focuses on a particular DNA structure called G-quadruplex (G4). These structures bear a specific sequence motif, which can be mapped genome-wide using computational methods. G4 motifs are found at very specific regions within the genome. Due to the specific locations, the evolutionary conservation and the strong stability of G4 structures they have been proposed to impact biological processes such as transcription, replication, recombination and telomere maintenance. The current idea is that those DNA structures serve as a regulatory tool in the cell to fine tune biological processes (positively and negatively) and by this change or alter the fate of the cell. It is still not clear when, where and why these structures form. If the hypothesis that G4 structures are fine tuning biological processes is correct it stands to reason that proteins are needed to form and unfold these structures in a timely manner. So far only a handful of such proteins were identified and characterized.
Due to the stability of G4 structures many helicases have been identified to disrupt G4 structures in vitro and in vivo. In the absence of these helicases mutations, deletions and increased recombination events accumulate. Interestingly, most of the helicases that have been described to regulate G4 structures have been implicated in human health. The direct link to G4 unwinding however is not fully understood, yet. In genetic disorders in which helicases are deficient, mutations are observed around regions with a strong potential to form G4 structures. This data suggests that helicases do not act at G4 structures globally, but only at a certain subset. How this specificity is achieved is not known.
Using bakers yeast (S. cerevisiae) as a model organism we aim to identify proteins that are important for G4 formation and unfolding. The characterization of these proteins is helping us to understand the question when and why these specific DNA structures form. We aim to learn how the cell uses G4 structures to up/down regulate transcription or to protect telomeres. Furthermore, by deleting or mutating these proteins, we want to investigate the question how changes in the G4 structure biology has an impact on other biological processes and genome stability. The overall aim of the proposal was to understand how G4 structures are regulated and how and these structures can lead to DNA damage (mutations and deletions).
