The aim of this thesis is to investigate the function of a number of
genes involved in mammalian DNA damage repair, in particular in repair of
DNA double-strand breaks (DSBs). Among a large number of different
damages that can be introduced to DNA, DSBs are especially toxic. If left
unrepaired, DSBs can trigger apoptosis or induce chromosomal
rearrangements that can lead to carcinogenesis. Two main pathways are
responsible for repair of DSBs: homologous recombination (HR) and nonhomologous
end joining (NHEJ). HR is generally an error-free mechanism
that restores missing information on the basis of homologous sequence
obtained from sister chromatid or homologous chromosome. By contrast,
NHEJ is generally error-prone. During repair by NHEJ the DNA ends can be
directly ligated or short stretches of homology at the ends can be used,
leading to deletions or insertions at the site of the break.
A number of genes have been identified as players in DSB repair, both
in prokaryotes and eukaryotes. Many of them are found in all the kingdoms of
life and are similar in aspects of their sequence and function, although there
are genes characteristic only for prokaryotes or eukaryotes.
Many subtle differences in function also emerge from studies on HR proteins
in different species. These differences might have appeared because of
diverse functions repair genes have to perform in more complexed organisms,
or because the initial function(s) of a gene has been distributed over multiple
paralogues.
Herein I concentrate on genes involved mainly in DSB repair via HR in
mammalian systems. Two members of the group of HR genes are studied:
Rad54 and its paralogue Rad548. Using mice and cells deficient in these
genes we try to define the role of both Rad54 and Rad54B in HR and their
contribution to other cellular processes. Additionally, we investigate the link
between Rad54 and Snm1, a gene originally identified as being important for
interstrand cross link (ICL) repair, with regard to ionizing radiation-induced
DNA damage repair