Genome. 1994 Aug;37(4):625-30. doi: 10.1139/g94-089.
Chromosomal and purified DNA methylation patterns were determined in the holocentric chromosomes of Megoura viciae by treatment with MspI and HpaII. Both enzymes produced a clear C-like banding pattern but widely digested one telomere of the X chromosome, which appeared as heterochromatic after C-banding treatment and brightly fluorescent after chromomycin A3 staining. Quantitative microfluorometric evaluations of DNA extraction performed on cytological preparations showed that both isoschizomers resulted in the same DNA extraction (about 30%). Contrary to what was found by in situ endonuclease treatment, the electrophoretic patterns of purified and digested DNA showed that digestion with MspI was slightly more extensive than that with HpaII in a zone of fragments ranging from 23 to 9 kb. This result indicates that aphid chromatin is not wholly unmethylated. The discrepancy between electrophoretic and cytological data has been explained by taking into consideration that DNA fragments with high molecular weights could be cleaved in situ by the enzymes but not extracted from the chromatin.
通过用 MspI 和 HpaII 处理，确定了全染色体的麦长管蚜的染色体和纯化的 DNA 甲基化模式。这两种酶都产生了清晰的 C 带模式，但广泛消化了 X 染色体的一个端粒，该端粒在 C 带处理后呈现异染色质，在用 chromomycin A3 染色后呈现明亮的荧光。对细胞学制剂上进行的 DNA 提取的定量微荧光评估表明，两种同工酶都导致相同的 DNA 提取（约 30%）。与通过原位内切酶处理发现的情况相反，纯化和消化的 DNA 的电泳模式表明，MspI 的消化比 HpaII 略广泛，在 23 到 9 kb 的片段范围内。这一结果表明，蚜虫染色质并非完全未甲基化。电泳和细胞学数据之间的差异通过考虑到高分子量的 DNA 片段可以在原位被酶切割但不能从染色质中提取出来而得到解释。
