The clustered DNA lesions are a characteristic feature of ionizing radiation and are defined as
two or more damage sites formed within 20 bps after the passage of a single radiation track. The clustered
DNA lesions are divided into two major groups: double-stranded breaks (DSBs) and non-DSB
clusters also known as Oxidatively-induced Clustered DNA Lesions (OCDLs), which could involve either
two opposing strands or the same strand. As irradiation is gaining greater interest in cancer treatment
as well as in imaging techniques, the detailed knowledge of its genotoxicity and the mechanisms of
repair of radiation-induced DNA damage remain issues to explore. In this review we look at the ways the
cell copes with clustered DNA lesions, especially with 5′,8-cyclo-2′-deoxypurines. As the base excision
repair deals with isolated lesions, complex damage is more difficult to repair. Depending on the number
of lesions within a cluster, their types and mutual distribution, long-patch BER or NER are activated.
During the repair of opposing lesions, DSBs could be generated, which are repaired either by nonhomologous
end joining (NHEJ) or homologous recombination (HR). The repair of individual lesions
within a cluster progresses gradually. This slower processing of particular damage might lead to severe
biological consequences such as misrepair, mutations and chromosomal rearrengement as it enhances the
plausibility of a cluster encountering a replication fork prior to its repair. The consequences of clustered
DNA lesions on cell survival and their relevance to the efficacy and safety of radiotherapy and radiodiagnosis
will also be discussed.
Determining dimension of the solution component that contains a computed zero of a polynomial system
