DNA is arguably the most important molecule found in any organism, as it contains all information to perform cellular functions and enables continuity of species. It is continuously exposed... Show more DNA is arguably the most important molecule found in any organism, as it contains all information to perform cellular functions and enables continuity of species. It is continuously exposed to DNA-damaging agents both from endogenous and exogenous sources. To protect DNA against these sources of DNA damage various DNA-repair mechanisms have evolved. If not properly repaired, DNA damage can lead to mutations that may eventually lead to cell-death or tumorigenesis. One of the most dangerous types of DNA damage is a DNA double-stranded break (DSB), in which a DNA molecule is broken into two pieces. Cells are equipped with several DSB-repair mechanisms to deal with this type of damage. Some of these mechanisms repair DSBs in an error-free fashion, while others are error-prone and can lead to the accumulation of mutations. Although accumulating many mutations in cells can lead to severely reduced cellular fitness, perfect DNA repair is less desirable in the long term as mutations allow for speciation and evolution to take place. The key question addressed in my thesis is which DSB-repair mechanisms organisms use to protect their genome against DSBs and I find alternative end-joining of DNA breaks to play a major role in maintaining genome stability. Show less
The genetic code of life is stored in DNA molecules that consist of two parallel strands of coupled nucleotides that form a DNA double helix. One of the most deleterious forms of DNA damage is a... Show moreThe genetic code of life is stored in DNA molecules that consist of two parallel strands of coupled nucleotides that form a DNA double helix. One of the most deleterious forms of DNA damage is a DNA double-strand break (DSB) in which both strands of the helix are broken. When not repaired adequately DSBs can lead to extensive loss of genetic information and/or genomic rearrangements, ultimately fueling genome instability, cellular dysfunction and malignant transformation. This thesis describes several studies conducted to examine how living organisms preserve their genetic material and how different DNA repair pathways influence genome stability. To study these questions the nematode C. elegans was used as a model organism, as it allows efficient genetic manipulation as well as in-depth genetic analysis of mutagenic processes. We exploited these unique attributes to i) convert these animals into in vivo sensors of DNA damage ii) identify factors not implicated in genome stability before, iii) unveil mechanisms that dictate DNA repair pathway choice, and iv) determine the biological consequences of endogenous barriers that impede DNA replication. Show less
