セミナー情報

A variety of endogenous and exogenous agents continuously damage genomes of living organisms. Adducts present in the DNA template during replication may cause transient replication fork blockage. Cells possess two strategies to tolerate lesions during replication Translesion Synthesis (TLS) and Damage Avoidance (DA). If both tolerance strategies fail, the replication fork may collapse and lead to cell death. While TLS pathways are responsible for the induction of the majority of point mutations, DA pathways are essentially error-free as they rely on homologous recombination strategies.
The genetics and biochemistry of TLS pathways has been uncovered during the last decade owing to the use of plasmid systems carrying single DNA lesions. We will review recent aspects of TLS pathways including the critical role of dNTP pool levels (Gon et.al. 2011). On the other hand, Damage Avoidance pathways take place within the context of a transiently blocked replication fork and entail homologous recombination between the lesion containing replication intermediate and its sister chromatid. Owing to the relatively small size of plasmids, single lesions in plasmids do not block the replication fork (Pages and Fuchs, 2003) and can thus not be used to study DA pathways. In order to overcome this difficulty we developed a new methodology that allows single DNA lesions to be inserted in the chromosome of living cells. The methodology is based upon the phage lambda site-specific recombination reaction that allows target a single lesion into a pre-defined locus in the E. coli chromosome.  The integration reaction is efficient and precise at nucleotide resolution level. We will present data showing the usefulness of this system to unravel the genetics of Damage Avoidance pathways (Pages et.al, 2012).