Focus on recombinational DNA repair

Abstract

The Juan March workshop on ‘Recombinational DNA Repair and its Links with DNA Replication and Chromosome Maintenance’ was held in Madrid, Spain, between 13 and 15 December 2004. The workshop was organized by S. Kowalczykowski, S. West, A. Aguilera and J. Alonso. ![][1] Homologous recombination (HR) has a crucial role in chromosome maintenance by promoting error‐free repair of DNA double‐strand breaks (DSBs) and single‐strand gaps. DNA strand breaks occur spontaneously during normal cellular processes, such as DNA replication, or when cells are treated with DNA damaging agents, and are essential intermediates in several programmed genome rearrangements. HR is also required for telomere maintenance in the absence of telomerase in eukaryotes. In Escherichia coli , most of the genes involved in HR were identified in screens for recombination‐defective mutants (rec genes). Similarly, screens for radiation‐sensitive mutants in budding yeast led to the discovery of the RAD52 epistasis group genes that define the main pathway for HR in eukaryotes. The RecA and Rad51 recombinases are central to the process of HR in prokaryotes and eukaryotes, respectively. Recombinases promote homologous pairing and strand exchange, which leads to recombination between the two interacting DNA molecules (Fig 1). However, the recombinases require several other proteins to accomplish strand exchange in vivo (Kowalczykowski, 2000; Krogh & Symington, 2004; West, 2003). The role of these accessory factors in facilitating the activity of the respective recombinase was one of the topics covered at the meeting. HR and nonhomologous end joining (NHEJ) are the main pathways for repairing DSBs in eukaryotic cells, but there are distinct sub‐pathways depending on the presence of one or two ends at the break site, or flanking homologies surrounding the DSB. The regulation of these pathways of DSB repair (DSBR) is an active area of investigation, as shown by the talks at this … [1]: /embed/graphic-1.gif