DNA Damage Laboratory of Food Science Department, Faculty of Pharmacy, Medical University of Lodz, ul. Muszynskiego 1, 90-151 Lodz, Poland.
Molecules. 2021 Jun 19;26(12):3750. doi: 10.3390/molecules26123750.
Restriction endonucleases (REs) are intra-bacterial scissors that are considered tools in the fight against foreign genetic material. SspI and BsmAI, examined in this study, cleave dsDNA at their site of recognition or within a short distance of it. Both enzymes are representatives of type II REs, which have played an extremely important role in research on the genetics of organisms and molecular biology. Therefore, the study of agents affecting their activity has become highly important. Ionizing radiation may damage basic cellular mechanisms by inducing lesions in the genome, with 5',8-cyclo-2'-deoxypurines (cdPus) as a model example. Since cdPus may become components of clustered DNA lesions (CDLs), which are unfavorable for DNA repair pathways, their impact on other cellular mechanisms is worthy of attention. This study investigated the influence of cdPus on the elements of the bacterial restriction-modification system. In this study, it was shown that cdPus present in DNA affect the activity of REs. SspI was blocked by any cdPu lesion present at the enzyme's recognition site. When lesions were placed near the recognition sequence, the SspI was inhibited up to 46%. Moreover, (5')-5',8-cyclo-2'-deoxyadenosine (ScdA) present in the oligonucleotide sequence lowered BsmAI activity more than (5')-5',8-cyclo-2'-deoxyadenosine (RcdA). Interestingly, in the case of 5',8-cyclo-2'-deoxyguanosine (cdG), both 5' and 5' diastereomers inhibited BsmAI activity (up to 55% more than cdA). The inhibition was weaker when cdG was present at the recognition site rather than the cleavage site.
限制内切酶（REs）是细菌内的剪刀，被认为是对抗外来遗传物质的工具。在本研究中检查了 SspI 和 BsmAI，它们在识别位点或其附近切割双链 DNA。这两种酶都是 II 型 REs 的代表，在研究生物体遗传学和分子生物学方面发挥了极其重要的作用。因此，研究影响其活性的因素变得非常重要。电离辐射可能通过在基因组中诱导损伤来破坏基本的细胞机制，以 5'，8-环-2'-脱氧嘌呤（cdPus）为例。由于 cdPus 可能成为不利的 DNA 修复途径的簇状 DNA 损伤（CDLs）的组成部分，因此它们对其他细胞机制的影响值得关注。本研究调查了 cdPus 对细菌限制修饰系统元件的影响。在这项研究中，表明存在于 DNA 中的 cdPus 会影响 REs 的活性。SspI 被存在于酶识别位点的任何 cdPu 损伤所阻断。当损伤位于识别序列附近时，SspI 的抑制率高达 46%。此外，寡核苷酸序列中存在的（5'）-5'，8-环-2'-脱氧腺苷（ScdA）降低了 BsmAI 的活性，比（5'）-5'，8-环-2'-脱氧腺苷（RcdA）更为明显。有趣的是，在 5'，8-环-2'-脱氧鸟嘌呤（cdG）的情况下，5'和 5'非对映异构体都抑制了 BsmAI 的活性（比 cdA 高多达 55%）。当 cdG 存在于识别位点而不是切割位点时，抑制作用较弱。
