Lalwani R, Maiti S, Mukherji S
Department of Biophysics, Chittaranjan National Cancer Institute, Calcutta, India.
J Photochem Photobiol B. 1995 Feb;27(2):117-22. doi: 10.1016/1011-1344(94)07065-v.
The formation of DNA-protein cross-links (DPCs), induced by irradiation with visible light, was studied in methylene blue-treated (MB-treated) chromatin and H1-depleted chromatin. The effects of the MB concentration and radiation dose were studied using sodium dodecylsulphate-chloroform-isoamyl alcohol assay and sodium dodecylsulphate-polyacrylamide gel electrophoresis. Under identical experimental conditions, DPC formation was less in H1-depleted chromatin (70%) than in chromatin (92%). The non-histone proteins and core proteins of chromatin contributed towards DPC formation. Of the core proteins, H2A was more cross-linked than H4, whereas the bands for H2B and H3 melted into one in chromatin and H1-depleted chromatin. In both cases, the gel pattern showed the appearance of two new protein bands with approximate molecular weights of 27 kDa and 29 kDa as a result of histone-histone cross-linking. Viscometric studies showed that the dissociation of the compact structure of chromatin in 2 M NaCl was more extensive in irradiated, MB-treated, H1-depleted chromatin than in irradiated, MB-treated chromatin, indicating a reduction in the amount of DPC formation in H1-depleted chromatin.
在亚甲蓝处理（MB处理）的染色质和H1缺失的染色质中，研究了可见光照射诱导的DNA-蛋白质交联（DPC）的形成。使用十二烷基硫酸钠-氯仿-异戊醇分析法和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳研究了MB浓度和辐射剂量的影响。在相同的实验条件下，H1缺失的染色质中DPC的形成（70%）比染色质中（92%）少。染色质的非组蛋白和核心蛋白对DPC的形成有贡献。在核心蛋白中，H2A比H4交联更多，而在染色质和H1缺失的染色质中，H2B和H3的条带融合成一条。在这两种情况下，凝胶图谱显示由于组蛋白-组蛋白交联，出现了两条新的蛋白质条带，分子量约为27 kDa和29 kDa。粘度测定研究表明，在2 M NaCl中，照射过的、MB处理过的、H1缺失的染色质中染色质紧密结构的解离比照射过的、MB处理过的染色质更广泛，这表明H1缺失的染色质中DPC的形成量减少。
