Mutation versus Repair: NEIL1 Removal of Hydantoin Lesions in Single-Stranded, Bulge, Bubble, and Duplex DNA Contexts

Xiaobei Zhao, Nirmala Krishnamurthy, Cynthia J. Burrows, Sheila S. David
2010 Biochemistry  
Human DNA glycosylase NEIL1 exhibits a superior ability to remove oxidized guanine lesions guanidinohydantoin (Gh) and spiroiminodihydantoin (Sp) from duplex DNA in comparison to other substrates. In the present work, Gh and Sp lesions in bubble, bulge and single-stranded DNA were found to be good substrates for NEIL1 but were typically excised at much slower rates than from canonical duplex substrates. A notable exception was the activity of NEIL1 on removal of Gh in bubble structures which
more » ... roaches that of the normal duplex substrate. The cleavage of Gh in the template strand of a replication or transcription bubble may prevent mutations associated with Gh during replication or transcription. However, hydantoin lesion removal in the absence of an opposite base may also result in strand breaks and potentially deletion and frameshift mutations. Consistent with this as a potential mechanism leading to an N-1 frameshift mutation, the nick left after the removal of the Gh lesion in a DNA bulge by NEIL1 was efficiently religated in the presence of polynucleotide kinase (PNK) and human DNA ligase III (Lig III). These results indicate that NEIL1 does not require a base opposite to identify and remove hydantoin lesions. Depending on the context, the glycosylase activity of NEIL1 may stall replication and prevent mutations or lead to inappropriate removal that may contribute to the mutational spectrum of these unusual lesions. Reactive oxygen species (ROS) are generated in mitochondria as byproducts of oxygen respiration. These radicals can be over-produced in cells under oxidative stress, due to inflammation, or as a result of exposure to toxic agents including ionizing radiation (1,2). Although ROS are produced as normal products of cellular metabolism, excessive free radicals can react with DNA, RNA, lipids and proteins, resulting in deleterious effects. Oxidative DNA damage, including abasic sites, base lesions, DNA strand breaks and DNA-protein cross-links, are implicated in a number of diseases such as cancer, aging and neurological diseases (3-6).
doi:10.1021/bi901852q pmid:20099873 pmcid:PMC2872175 fatcat:vglqyzpq45c4rctfdykxhkkdre