Homology-dependent maternal inhibition of developmental excision of internal eliminated sequences in Paramecium tetraurelia
Homology-dependent maternal inhibition of developmental excision of internal eliminated sequences in Paramecium tetraurelia
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DOI：
10.1128/mcb.18.12.7075
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发表时间：
1998-12-01
影响因子：
5.3
通讯作者：
Meyer, E
中科院分区：
文献类型：
--
作者：
Duharcourt, S;Keller, AM;Meyer, E
在性行为发生后的多基因组体细胞大核发育过程中，纤毛虫生殖系基因组中数以千计的单拷贝内部消除序列(IESS)被删除。草履虫是一种短的非编码元件，经常中断编码序列。除了5‘-TA-3’侧翼的直接重复序列外，在已测序的Less中没有发现绝对保守的序列元件；它们的特异性识别和精确消除的机制尚不清楚。以前的工作已经揭示了切除的表观遗传控制的存在。结果表明，营养大核中一种IES的存在，导致在下一有性世代的新大核发育过程中，对同一元件的摘除产生特异性的抑制。我们通过研究13种不同的IESS对大核转化的影响，评估了这种跨核母体对照的通用性和序列特异性，我们发现至少有5种可以在新的大核基因组中保持；序列特异性在基因之间和同一基因中不同的IESS之间都是完全的。在所有情况下，切除抑制的程度与母体IES的拷贝数有关，但每个IES都表现出特有的抑制效率，当抑制正常边界之间的切除时，发现从两个Iess中切除了较短的内部IES样片段。现有数据表明，这些母性效应的序列特异性是由同源核酸之间的配对相互作用介导的。
Thousands of single-copy internal eliminated sequences (IESs) are excised from the germ line genome of ciliates during development of the polygenomic somatic macronucleus, following sexual events. Paramecium IESs are short, noncoding elements that frequently interrupt coding sequences. No absolutely conserved sequence element, other than flanking 5'-TA-3' direct repeats, has been identified among sequenced IESs; the mechanisms of their specific recognition and precise elimination are unknown. Previous work has revealed the existence of an epigenetic control of excision. It was shown that the presence of one IES in the vegetative macronucleus results in a specific inhibition of the excision of the same element during the development of a new macronucleus, in the following sexual generation. We have assessed the generality and sequence specificity of this transnuclear maternal control by studying the effects of macronuclear transformation with 13 different IESs, We show that at least five of them can be maintained in the new macronuclear genome; sequence specificity is complete both between genes and between different IESs in the same gene. In all cases, the degree of excision inhibition correlates with the copy number of the maternal IES, but each IES shows a characteristic inhibition efficiency, Short internal IES-like segments were found to be excised from two of the IESs when excision between normal boundaries was inhibited. Available data suggest that the sequence specificity of these maternal effects is mediated by pairing interactions between homologous nucleic acids.