Peoples O P, Hardman N
Nucleic Acids Res. 1983 Nov 25;11(22):7777-88. doi: 10.1093/nar/11.22.7777.
A significant portion (20%) of the Physarum genome can be isolated as a HpaII-resistant, methylated fraction. Cloned DNA probes containing highly-repeated sequences derived from this fraction were used to define the pattern of structural organisation of homologous repeats in Physarum genomic DNA. It is shown that the probes detect an abundant, methylated family of sequences with an estimated genomic repetition frequency greater than 2100, derived from a large repeated element whose length exceeds 5.8kb. Sequences comprising the long repetitive element dominate the HpaII-resistant compartment and account for between 4-20% of the Physarum genome. Detailed restriction/hybridisation analysis of cloned DNA segments derived from this compartment shows that HpaII/MspI restriction sites within some copies of the long repeated sequence are probably deleted by mutation. Additionally, segments of the repeat are often found in different organisational patterns that represent scrambled versions of its basic structure, and which are presumed to have arisen as a result of recombinational rearrangement in situ in the Physarum genome. Preliminary experiments indicate that the sequences are transcribed and that the structural properties of the repeat bear some resemblance to those of transposable genetic elements defined in other eukaryotic species.
绒泡菌基因组中有很大一部分（20%）可作为对HpaII有抗性的甲基化部分被分离出来。含有源自该部分的高度重复序列的克隆DNA探针被用于确定绒泡菌基因组DNA中同源重复序列的结构组织模式。结果表明，这些探针检测到一个丰富的甲基化序列家族，其估计的基因组重复频率大于2100，源自一个长度超过5.8kb的大型重复元件。构成长重复元件的序列在对HpaII有抗性的部分中占主导地位，占绒泡菌基因组的4 - 20%。对源自该部分的克隆DNA片段进行详细的限制性内切酶/杂交分析表明，长重复序列的某些拷贝中的HpaII/MspI限制性位点可能因突变而缺失。此外，重复序列的片段经常以不同的组织模式出现，这些模式代表其基本结构的混乱版本，推测是由于绒泡菌基因组中就地重组重排而产生的。初步实验表明这些序列是可转录的，并且该重复序列的结构特性与其他真核物种中定义的转座遗传元件的结构特性有一些相似之处。
