Role of the Nucleotide Excision Repair endonuclease XPF in the kinetoplastid parasite Trypanosoma brucei

Abstract

The nucleotide excision repair (NER) mechanism is responsible for the removal of bulky DNA damage such as pyrimidine dimers induced by ultraviolet light. The NER pathway detects such lesions and excises the damaged strand through incisions at 5 and 3 of the damage. The 5 incision is catalyzed by a heterodimeric endonuclease composed of XPF (catalytic subunit) and ERCC1 (non-catalytic). Here, we show that the genome of Trypanosoma brucei, the causal agent of human African trypanosomiasis or sleeping sickness, codes for an XPF ortholog. RNAi silencing of TbXPF sensitizes cells to UV irradiation, thus providing evidence that NER operates in these parasites. In addition, TbXPF confers protection against intra- and inter-strand crosslinks induced by cisplatin and mitomycin C respectively. Consistent with a role in DNA repair, XPF localizes to the cell nucleus, and is found associated to nucleoplasmic and nucleolar regions. The presence of a functional NER pathway in trypanosomes suggests that in vivo, they are susceptible to undergo replication and transcription-blocking DNA damages. The results obtained with various antitumor agents provide proof of concept for the potential of NER inhibition as a means to improve antiparasitic therapies.