Identification of Novel Factors Involved in Interstrand Cross-link Repair

The hallmark of Fanconi anemia (FA) cells is their hypersensitivity to DNA interstrand cross-linking (ICL) agents. It is known that all the FA proteins cooperate in a common pathway that is activated after treatment with ICL agents, but exactly how this pathway leads to DNA repair is still obscure. In Drosophila melanogaster, the mus308 mutation leads to marked sensitivity to ICLs, thus resembling FA cells. The C-terminal portion of the Mus308 polypeptide encodes a DNA polymerase, while the N-terminal portion encodes a DNA helicase. We cloned three mus308 related genes: POLQ, HEL308 and POLN both from human and mouse. We purified recombinant proteins and assayed their activity "in vitro". We also analized their expression "in vivo", both in mouse and human tissues. We will present our recent results suggesting that human POLN might be involved in ICL repair, thus possibly interacting with the FA pathway. We also studied the roles of FA proteins and the Mus308 related genes in the genetically amenable multicellular model system C. elegans, by characterizing the phenotype of worms that do not express these genes and testing whether they mimic the FA cellular defects. Our goal is to find a connection between the FA signal transduction pathway and the enzymes that physically participate in the removal of ICLs.