Nucleotide Excision Repair Coupled to Chromatin Assembly

The packaging of DNA into a chromatin structure within the eukaryotic nucleus can affect processes such as DNA replication, transcription, recombination and repair. During nucleotide excision repair (NER), a major DNA repair pathway, rearrangements of the nucleosomal organisation are observed (1 ). These rearrangements can be envisioned as the rapid succession of disassembly and reassembly events. A tight co-ordination between the actual DNA repair event and the chromatin assembly process will be critical to fully restore a functional genome. A step toward the dissection of these events was recently accomplished by the development of an assay for both chromatin assembly and NER on the same DNA molecules in cell-free systems competent for the two processes (2 ,3 ). Both chromatin assembly and NER have been independently analysed in a variety of cell-free systems. Efficient chromatin assembly can be reproduced in crude extracts derived from Xenopus oocytes or eggs (4 –7 ), Drosophila embryos (8 –10 ), or from human cells (11 –14 ). Extracts competent for the NER process can be derived from a variety of cultured mammalian cells (15 ,16 ), cultured Drosophila cells (17 ), and Xenopus eggs (18 ).