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Conservation and divergence of the histone code in nucleomorphs

BACKGROUND: Nucleomorphs, the remnant nuclei of photosynthetic algae that have become endosymbionts to other eukaryotes, represent a unique example of convergent reductive genome evolution in eukaryotes, having evolved independently on two separate occasions in chlorarachniophytes and cryptophytes....

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Detalles Bibliográficos
Autores principales: Marinov, Georgi K., Lynch, Michael
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4822330/
https://www.ncbi.nlm.nih.gov/pubmed/27048461
http://dx.doi.org/10.1186/s13062-016-0119-4
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author Marinov, Georgi K.
Lynch, Michael
author_facet Marinov, Georgi K.
Lynch, Michael
author_sort Marinov, Georgi K.
collection PubMed
description BACKGROUND: Nucleomorphs, the remnant nuclei of photosynthetic algae that have become endosymbionts to other eukaryotes, represent a unique example of convergent reductive genome evolution in eukaryotes, having evolved independently on two separate occasions in chlorarachniophytes and cryptophytes. The nucleomorphs of the two groups have evolved in a remarkably convergent manner, with numerous very similar features. Chief among them is the extreme reduction and compaction of nucleomorph genomes, with very small chromosomes and extremely short or even completely absent intergenic spaces. These characteristics pose a number of intriguing questions regarding the mechanisms of transcription and gene regulation in such a crowded genomic context, in particular in terms of the functioning of the histone code, which is common to almost all eukaryotes and plays a central role in chromatin biology. RESULTS: This study examines the sequences of nucleomorph histone proteins in order to address these issues. Remarkably, all classical transcription- and repression-related components of the histone code seem to be missing from chlorarachniophyte nucleomorphs. Cryptophyte nucleomorph histones are generally more similar to the conventional eukaryotic state; however, they also display significant deviations from the typical histone code. Based on the analysis of specific components of the code, we discuss the state of chromatin and the transcriptional machinery in these nuclei. CONCLUSIONS: The results presented here shed new light on the mechanisms of nucleomorph transcription and gene regulation and provide a foundation for future studies of nucleomorph chromatin and transcriptional biology. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13062-016-0119-4) contains supplementary material, which is available to authorized users.
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spelling pubmed-48223302016-04-07 Conservation and divergence of the histone code in nucleomorphs Marinov, Georgi K. Lynch, Michael Biol Direct Research BACKGROUND: Nucleomorphs, the remnant nuclei of photosynthetic algae that have become endosymbionts to other eukaryotes, represent a unique example of convergent reductive genome evolution in eukaryotes, having evolved independently on two separate occasions in chlorarachniophytes and cryptophytes. The nucleomorphs of the two groups have evolved in a remarkably convergent manner, with numerous very similar features. Chief among them is the extreme reduction and compaction of nucleomorph genomes, with very small chromosomes and extremely short or even completely absent intergenic spaces. These characteristics pose a number of intriguing questions regarding the mechanisms of transcription and gene regulation in such a crowded genomic context, in particular in terms of the functioning of the histone code, which is common to almost all eukaryotes and plays a central role in chromatin biology. RESULTS: This study examines the sequences of nucleomorph histone proteins in order to address these issues. Remarkably, all classical transcription- and repression-related components of the histone code seem to be missing from chlorarachniophyte nucleomorphs. Cryptophyte nucleomorph histones are generally more similar to the conventional eukaryotic state; however, they also display significant deviations from the typical histone code. Based on the analysis of specific components of the code, we discuss the state of chromatin and the transcriptional machinery in these nuclei. CONCLUSIONS: The results presented here shed new light on the mechanisms of nucleomorph transcription and gene regulation and provide a foundation for future studies of nucleomorph chromatin and transcriptional biology. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13062-016-0119-4) contains supplementary material, which is available to authorized users. BioMed Central 2016-04-05 /pmc/articles/PMC4822330/ /pubmed/27048461 http://dx.doi.org/10.1186/s13062-016-0119-4 Text en © Marinov and Lynch. 2016 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research
Marinov, Georgi K.
Lynch, Michael
Conservation and divergence of the histone code in nucleomorphs
title Conservation and divergence of the histone code in nucleomorphs
title_full Conservation and divergence of the histone code in nucleomorphs
title_fullStr Conservation and divergence of the histone code in nucleomorphs
title_full_unstemmed Conservation and divergence of the histone code in nucleomorphs
title_short Conservation and divergence of the histone code in nucleomorphs
title_sort conservation and divergence of the histone code in nucleomorphs
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4822330/
https://www.ncbi.nlm.nih.gov/pubmed/27048461
http://dx.doi.org/10.1186/s13062-016-0119-4
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