Small-scale extracts for the study of nucleotide excision repair and non-homologous end joining

The repair of DNA by nucleotide excision repair (NER) and non-homologous end joining (NHEJ) is essential for maintenance of genomic integrity and cell viability. Examination of NHEJ and NER in vitro using cell-free extracts has led to a deeper under- standing of the biochemical mechanisms that underlie these processes. Current methods for production of whole-cell extracts (WCEs) to inves- tigate NER and NHEJ start with one or more liters of culture containing 1-5 3109 cells. Here, we describe a small-scale method for production of WCE that can be used to study NER. We also describe a rapid, small-scale method for the preparation of WCE that can be used in the study of NHEJ. These methods require less time, 20- to 1000-fold fewer cells than large-scale extracts, facilitate examination of numerous samples and are ideal for such appli- cations as the study of host-virus interactions and analysis of mutant cell lines.