DNA double strand breaks and chromosomal aberrations

DNA double strand breaks (DSBs) are ultimate lesions for the formation of chromosomal aberrations (CAs). The formation of CAs is dependent on many factors; some of these are discussed in this review. FISH methodologies have uncovered CA types which cannot be seen with the classical staining methods, and thereby widened our understanding of the origin of CAs. The mobility of DSBs in interphase nuclei is limited. This makes it especially difficult to understand the origin of complex CAs involving many chromosomes. Even using high-resolution mBAND FISH to analyze CAs, the ratio of inter-/intrachromosomal CAs is higher than 1. From this it was postulated that only a subset of DSBs, namely, complex or clustered DSBs give rise mainly to interchromosomal CAs. The finding that endonucleases induce CAs does not fit the idea of complex DSBs being responsible for CA. Probably it is the proximity and not the complexity of DSBs which leads to CA.