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Biogenesis of Developmental Master Regulatory 27nt-RNAs in Stylonychia—Can Coding RNA Turn into Non-Coding?
In the ciliate Stylonychia, somatic macronuclei differentiate from germline micronuclei during sexual reproduction, accompanied by developmental sequence reduction. Concomitantly, over 95% of micronuclear sequences adopt a heterochromatin structure characterized by the histone variant H3.4 and H3K27...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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MDPI
2019
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6896033/ https://www.ncbi.nlm.nih.gov/pubmed/31752243 http://dx.doi.org/10.3390/genes10110940 |
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author | Postberg, Jan Weil, Patrick Philipp Pembaur, Anton |
author_facet | Postberg, Jan Weil, Patrick Philipp Pembaur, Anton |
author_sort | Postberg, Jan |
collection | PubMed |
description | In the ciliate Stylonychia, somatic macronuclei differentiate from germline micronuclei during sexual reproduction, accompanied by developmental sequence reduction. Concomitantly, over 95% of micronuclear sequences adopt a heterochromatin structure characterized by the histone variant H3.4 and H3K27me3. RNAi-related genes and histone variants dominate the list of developmentally expressed genes. Simultaneously, 27nt-ncRNAs that match sequences retained in new macronuclei are synthesized and bound by PIWI1. Recently, we proposed a mechanistic model for ‘RNA-induced DNA replication interference’ (RIRI): during polytene chromosome formation PIWI1/27nt-RNA-complexes target macronucleus-destined sequences (MDS) by base-pairing and temporarily cause locally stalled replication. At polytene chromosomal segments with ongoing replication, H3.4K27me3-nucleosomes become selectively deposited, thus dictating the prospective heterochromatin structure of these areas. Consequently, these micronucleus-specific sequences become degraded, whereas 27nt-RNA-covered sites remain protected. However, the biogenesis of the 27nt-RNAs remains unclear. It was proposed earlier that in stichotrichous ciliates 27nt-RNA precursors could derive from telomere-primed bidirectional transcription of nanochromosomes and subsequent Dicer-like (DCL) activity. As a minimalistic explanation, we propose here that the 27nt-RNA precursor could rather be mRNA or pre-mRNA and that the transition of coding RNA from parental macronuclei to non-coding RNAs, which act in premature developing macronuclei, could involve RNA-dependent RNA polymerase (RDRP) activity creating dsRNA intermediates prior to a DCL-dependent pathway. Interestingly, by such mechanism the partition of a parental somatic genome and possibly also the specific nanochromosome copy numbers could be vertically transmitted to the differentiating nuclei of the offspring. |
format | Online Article Text |
id | pubmed-6896033 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2019 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-68960332019-12-24 Biogenesis of Developmental Master Regulatory 27nt-RNAs in Stylonychia—Can Coding RNA Turn into Non-Coding? Postberg, Jan Weil, Patrick Philipp Pembaur, Anton Genes (Basel) Review In the ciliate Stylonychia, somatic macronuclei differentiate from germline micronuclei during sexual reproduction, accompanied by developmental sequence reduction. Concomitantly, over 95% of micronuclear sequences adopt a heterochromatin structure characterized by the histone variant H3.4 and H3K27me3. RNAi-related genes and histone variants dominate the list of developmentally expressed genes. Simultaneously, 27nt-ncRNAs that match sequences retained in new macronuclei are synthesized and bound by PIWI1. Recently, we proposed a mechanistic model for ‘RNA-induced DNA replication interference’ (RIRI): during polytene chromosome formation PIWI1/27nt-RNA-complexes target macronucleus-destined sequences (MDS) by base-pairing and temporarily cause locally stalled replication. At polytene chromosomal segments with ongoing replication, H3.4K27me3-nucleosomes become selectively deposited, thus dictating the prospective heterochromatin structure of these areas. Consequently, these micronucleus-specific sequences become degraded, whereas 27nt-RNA-covered sites remain protected. However, the biogenesis of the 27nt-RNAs remains unclear. It was proposed earlier that in stichotrichous ciliates 27nt-RNA precursors could derive from telomere-primed bidirectional transcription of nanochromosomes and subsequent Dicer-like (DCL) activity. As a minimalistic explanation, we propose here that the 27nt-RNA precursor could rather be mRNA or pre-mRNA and that the transition of coding RNA from parental macronuclei to non-coding RNAs, which act in premature developing macronuclei, could involve RNA-dependent RNA polymerase (RDRP) activity creating dsRNA intermediates prior to a DCL-dependent pathway. Interestingly, by such mechanism the partition of a parental somatic genome and possibly also the specific nanochromosome copy numbers could be vertically transmitted to the differentiating nuclei of the offspring. MDPI 2019-11-18 /pmc/articles/PMC6896033/ /pubmed/31752243 http://dx.doi.org/10.3390/genes10110940 Text en © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Review Postberg, Jan Weil, Patrick Philipp Pembaur, Anton Biogenesis of Developmental Master Regulatory 27nt-RNAs in Stylonychia—Can Coding RNA Turn into Non-Coding? |
title | Biogenesis of Developmental Master Regulatory 27nt-RNAs in Stylonychia—Can Coding RNA Turn into Non-Coding? |
title_full | Biogenesis of Developmental Master Regulatory 27nt-RNAs in Stylonychia—Can Coding RNA Turn into Non-Coding? |
title_fullStr | Biogenesis of Developmental Master Regulatory 27nt-RNAs in Stylonychia—Can Coding RNA Turn into Non-Coding? |
title_full_unstemmed | Biogenesis of Developmental Master Regulatory 27nt-RNAs in Stylonychia—Can Coding RNA Turn into Non-Coding? |
title_short | Biogenesis of Developmental Master Regulatory 27nt-RNAs in Stylonychia—Can Coding RNA Turn into Non-Coding? |
title_sort | biogenesis of developmental master regulatory 27nt-rnas in stylonychia—can coding rna turn into non-coding? |
topic | Review |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6896033/ https://www.ncbi.nlm.nih.gov/pubmed/31752243 http://dx.doi.org/10.3390/genes10110940 |
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