Maternal noncoding transcripts antagonize the targeting of DNA elimination by scanRNAs in Paramecium tetraurelia
Maternal noncoding transcripts antagonize the targeting of DNA elimination by scanRNAs in Paramecium tetraurelia
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DOI：
10.1101/gad.473008
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发表时间：
2008-06-01
影响因子：
10.5
通讯作者：
Duharcourt, Sandra
中科院分区：
文献类型：
--
作者：
Lepere, Gersende;Betermier, Mireille;Duharcourt, Sandra
交配后，纤毛虫的生殖系基因组在从生殖系微核发育成体细胞巨核的过程中发生了广泛的重排。在四虫草履虫中，单拷贝内部消除序列（IESs）被精确地从编码序列和基因间区切除。对于ess的一个子集，将IES序列引入母系大核特异性地抑制了发育中的合子大核中同源IES的切除，这表明切除的表观遗传调控涉及种系和体细胞基因组的全局比较。在微核减数分裂过程中，通过发育调节的RNAi途径产生的扫描rna （scnRNAs）被认为介导这种跨核交叉对话。在本研究中，显微注射实验提供了25个核苷酸（nt）的scnRNAs促进IES切除的直接证据。我们进一步表明，非编码rna是由体细胞母系基因组产生的，无论是在营养生长期间还是在性活动期间。当含有IES的母体体细胞转录本被涉及23-nt sinas的不同RNAi途径降解时，母体对IES切除的抑制就会被消除。结果强烈支持scnRNA/大核RNA扫描模型，其中在减数分裂期间，在诱导缺失的scnRNA和来自母体大核的拮抗转录物之间发生自然的基因组减数，调节合子基因组的重排。
The germline genome of ciliates is extensively rearranged during the development of a new somatic macronucleus from the germline micronucleus, after sexual events. In Paramecium tetraurelia, single-copy internal eliminated sequences (IESs) are precisely excised from coding sequences and intergenic regions. For a subset of IESs, introduction of the IES sequence into the maternal macronucleus specifically inhibits excision of the homologous IES in the developing zygotic macronucleus, suggesting that epigenetic regulation of excision involves a global comparison of germline and somatic genomes. ScanRNAs (scnRNAs) produced during micronuclear meiosis by a developmentally regulated RNAi pathway have been proposed to mediate this transnuclear cross-talk. In this study, microinjection experiments provide direct evidence that 25-nucleotide (nt) scnRNAs promote IES excision. We further show that noncoding RNAs are produced from the somatic maternal genome, both during vegetative growth and during sexual events. Maternal inhibition of IES excision is abolished when maternal somatic transcripts containing an IES are targeted for degradation by a distinct RNAi pathway involving 23-nt siRNAs. The results strongly support a scnRNA/macronuclear RNA scanning model in which a natural genomic subtraction, occurring during meiosis between deletion-inducing scnRNAs and antagonistic transcripts from the maternal macronucleus, regulates rearrangements of the zygotic genome.