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内容記述 |
DNA damage poses significant threats to biological systems, potentially leading to severe consequences. Recent research has yielded new insights into the frequency of DNA damage occurrence and the mechanisms of its repair. On a daily basis, DNA can undergo damage 50,000 to 500,000 times due to normal cellular metabolic processes and external factors. Most of these damages are efficiently repaired by cellular DNA repair mechanisms and thus do not have major impacts on the organism. However, if some damages persist unrepaired, they can contribute to the onset of diseases such as cancer and aging. There are various types of DNA damage, many of which are induced by external factors such as environmental mutagens and radiation. However, the exact frequency and repair mechanisms of these individual DNA damages remain incompletely understood. This study focuses on cluster damage and DNA-protein crosslink (DPC) damage, which can lead to mutations and carcinogenesis. Cluster damage involves simultaneous damage to multiple bases within DNA, making its quantification challenging. Traditional methods of analyzing these damages individually have been limited. Techniques such as fluorescence microscopy struggle to measure the distances between cluster damages, making it difficult to distinguish whether they occur within tens of base pairs or are spatially distributed over chromatin loops ranging from thousands to tens of thousands of base pairs. To address this, we utilized atomic force microscopy (AFM), which allows for nanometer-scale analysis, to observe and categorize DNA damages. This approach enabled us to elucidate the prevalence of different DNA damage types, assess their repairability, and identify DNA damages that persist long-term in living organisms. DPCs, where DNA and proteins are covalently bonded, have also been difficult to analyze in detail using traditional methods. Conventional techniques such as alkaline elution and comet assays, which measure the amount of DNA bound to DPCs or their electrophoretic mobility, often introduce errors and fail to provide information on the type and position of the DPCs. By classifying and analyzing these DPCs, we obtained new information revealing that different proteins involved in DPCs and the presence or absence of strand breaks influence the repair mechanisms and result in varying biological impacts. Our findings indicate that what was previously categorized broadly as cluster damage or DPC damage actually consists of a diverse array of structures with varying biological significance. The establishment of novel analytical methods has allowed us to identify specific types of DNA damage that may have significant implications for cellular health. This presentation will report on these findings. |
