Discussion

DNA lesions that lead to helix distortions or block replication signalise to Nucleotide Excision Repair (NER) activation. Two sub-pathways act in the first step involving recognition of the DNA lesion: global genomic-NER (GG- NER) and transcription-coupled NER (TC-NER). The way the pathway works in T. brucei is still unclear as some components are missing. With the aim to identify the cellular components involved in TC-NER in T. brucei mutants for CSB, the protein that recognizes a stalled RNA Polymerase, were generated. CSB knockouts show increased susceptibility to UV treatment. This effect in more pronounced in the presence of Caffeine. The over-expression of CSB results in no difference in the susceptibility or resistance to UV treatment. To better understand the role of each component, myc-tagged CSB, XPC, XPG and XPBz variants were used for subcellular localization. They are nuclear localized and no change in the subcellular localization was observed after treatment with UV. Our results suggest a neofunctionalisation of the machinery in trymanosomatids.