Meyer E, Butler A, Dubrana K, Duharcourt S, Caron F
Laboratoire de Génétique Moléculaire, ENS, Paris, France.
Mol Cell Biol. 1997 Jul;17(7):3589-99. doi: 10.1128/MCB.17.7.3589.
In ciliates, the germ line genome is extensively rearranged during the development of the somatic macronucleus from a mitotic product of the zygotic nucleus. Germ line chromosomes are fragmented in specific regions, and a large number of internal sequence elements are eliminated. It was previously shown that transformation of the vegetative macronucleus of Paramecium primaurelia with a plasmid containing a subtelomeric surface antigen gene can affect the processing of the homologous germ line genomic region during development of a new macronucleus in sexual progeny of transformed clones. The gene and telomere-proximal flanking sequences are deleted from the new macronuclear genome, although the germ line genome remains wild type. Here we show that plasmids containing nonoverlapping segments of the same genomic region are able to induce similar terminal deletions; the locations of deletion end points depend on the particular sequence used. Transformation of the maternal macronucleus with a sequence internal to a macronuclear chromosome also causes the occurrence of internal deletions between short direct repeats composed of alternating thymines and adenines. The epigenetic influence of maternal macronuclear sequences on developmental rearrangements of the zygotic genome thus appears to be both sequence specific and general, suggesting that this trans-nucleus effect is mediated by pairing of homologous sequences.
在纤毛虫中，生殖系基因组在合子核有丝分裂产物发育成体细胞大核的过程中会发生广泛重排。生殖系染色体在特定区域断裂，大量内部序列元件被消除。先前的研究表明，用含有亚端粒表面抗原基因的质粒转化双小核草履虫的营养大核，可影响转化克隆有性后代新大核发育过程中同源生殖系基因组区域的加工。新的大核基因组中该基因和端粒近端侧翼序列被删除，尽管生殖系基因组仍为野生型。在此我们表明，含有同一基因组区域非重叠片段的质粒能够诱导相似的末端缺失；缺失端点的位置取决于所使用的特定序列。用大核染色体内的一段序列转化母本大核，也会导致由交替的胸腺嘧啶和腺嘌呤组成的短直接重复序列之间出现内部缺失。因此，母本大核序列对合子基因组发育重排的表观遗传影响似乎既是序列特异性的，也是普遍存在的，这表明这种跨核效应是由同源序列配对介导的。
