Dissemin is shutting down on January 1st, 2025

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Cold Spring Harbor Laboratory Press, Genes & Development, 11(22), p. 1501-1512, 2008

DOI: 10.1101/gad.473008

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Maternal noncoding transcripts antagonize the targeting of DNA elimination by scanRNAs in Paramecium tetraurelia

Journal article published in 2008 by Gersende Lepere, Mireille Bétermier, Eric Meyer, Sandra Duharcourt
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

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.