Characterization of novel factors involved in interstrand cross-link sensitivity

Repair of DNA interstrand cross-links (ICLs) is a challenging problem for cells. Many human gene products influence sensitivity to crosslinking agents, but the mechanisms of ICL repair are unknown. Fanconi anemia (FA) patients are hypersensitive to 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 D. melanogaster, the mus308 mutation leads to marked sensitivity to ICLs. The Mus308 gene is unusual in encoding both a family A DNA polymerase domain and a DNA/RNA helicase domain. As a step towards isolating proteins involved in DNA crosslink repair, 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. Our recent results suggest that human POLN might be involved in ICL repair. 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.