Persistent DNA Damage Foci and DNA Replication with a Broken Chromosome in the African Trypanosome

ABSTRACT Damaged DNA typically imposes stringent controls on eukaryotic cell cycle progression, ensuring faithful transmission of genetic material. Some DNA breaks, and the resulting rearrangements, are advantageous, however. For example, antigenic variation in the parasitic African trypanosome, Try...

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Autores principales:	Lucy Glover, Catarina A. Marques, Olga Suska, David Horn
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Lenguaje:	EN
Publicado:	American Society for Microbiology 2019
Materias:	RPA2 damage response telomere Microbiology QR1-502
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spelling	oai:doaj.org-article:143e3366d41c43898cd4efaedcc625dd2021-11-15T16:22:08ZPersistent DNA Damage Foci and DNA Replication with a Broken Chromosome in the African Trypanosome10.1128/mBio.01252-192150-7511https://doaj.org/article/143e3366d41c43898cd4efaedcc625dd2019-08-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01252-19https://doaj.org/toc/2150-7511ABSTRACT Damaged DNA typically imposes stringent controls on eukaryotic cell cycle progression, ensuring faithful transmission of genetic material. Some DNA breaks, and the resulting rearrangements, are advantageous, however. For example, antigenic variation in the parasitic African trypanosome, Trypanosoma brucei, relies upon homologous recombination-based rearrangements of telomeric variant surface glycoprotein (VSG) genes, triggered by breaks. Surprisingly, trypanosomes with a severed telomere continued to grow while progressively losing subtelomeric DNA, suggesting a nominal telomeric DNA damage checkpoint response. Here, we monitor the single-stranded DNA-binding protein replication protein A (RPA) in response to induced, locus-specific DNA breaks in T. brucei. RPA foci accumulated at nucleolar sites following a break within ribosomal DNA and at extranucleolar sites following a break elsewhere, including adjacent to transcribed or silent telomeric VSG genes. As in other eukaryotes, RPA foci were formed in S phase and γH2A and RAD51 damage foci were disassembled prior to mitosis. Unlike in other eukaryotes, however, and regardless of the damaged locus, RPA foci persisted through the cell cycle, and these cells continued to replicate their DNA. We conclude that a DNA break, regardless of the damaged locus, fails to trigger a stringent cell cycle checkpoint in T. brucei. This DNA damage tolerance may facilitate the generation of virulence-enhancing genetic diversity, within subtelomeric domains in particular. Stringent checkpoints may be similarly lacking in some other eukaryotic cells. IMPORTANCE Chromosome damage must be repaired to prevent the proliferation of defective cells. Alternatively, cells with damage must be eliminated. This is true of human and several other cell types but may not be the case for single-celled parasites, such as trypanosomes. African trypanosomes, which cause lethal diseases in both humans and livestock, can actually exploit chromosomal damage to activate new surface coat proteins and to evade host immune responses, for example. We monitored responses to single chromosomal breaks in trypanosomes using a DNA-binding protein that, in response to DNA damage, forms nuclear foci visible using a microscope. Surprisingly, and unlike what is seen in mammalian cells, these foci persist while cells continue to divide. We also demonstrate chromosome replication even when one chromosome is broken. These results reveal a remarkable degree of damage tolerance in trypanosomes, which may suit the lifestyle of a single-celled parasite, potentially facilitating adaptation and enhancing virulence.Lucy GloverCatarina A. MarquesOlga SuskaDavid HornAmerican Society for MicrobiologyarticleRPA2damage responsetelomereMicrobiologyQR1-502ENmBio, Vol 10, Iss 4 (2019)
institution	DOAJ
collection	DOAJ
language	EN
topic	RPA2 damage response telomere Microbiology QR1-502
spellingShingle	RPA2 damage response telomere Microbiology QR1-502 Lucy Glover Catarina A. Marques Olga Suska David Horn Persistent DNA Damage Foci and DNA Replication with a Broken Chromosome in the African Trypanosome
description	ABSTRACT Damaged DNA typically imposes stringent controls on eukaryotic cell cycle progression, ensuring faithful transmission of genetic material. Some DNA breaks, and the resulting rearrangements, are advantageous, however. For example, antigenic variation in the parasitic African trypanosome, Trypanosoma brucei, relies upon homologous recombination-based rearrangements of telomeric variant surface glycoprotein (VSG) genes, triggered by breaks. Surprisingly, trypanosomes with a severed telomere continued to grow while progressively losing subtelomeric DNA, suggesting a nominal telomeric DNA damage checkpoint response. Here, we monitor the single-stranded DNA-binding protein replication protein A (RPA) in response to induced, locus-specific DNA breaks in T. brucei. RPA foci accumulated at nucleolar sites following a break within ribosomal DNA and at extranucleolar sites following a break elsewhere, including adjacent to transcribed or silent telomeric VSG genes. As in other eukaryotes, RPA foci were formed in S phase and γH2A and RAD51 damage foci were disassembled prior to mitosis. Unlike in other eukaryotes, however, and regardless of the damaged locus, RPA foci persisted through the cell cycle, and these cells continued to replicate their DNA. We conclude that a DNA break, regardless of the damaged locus, fails to trigger a stringent cell cycle checkpoint in T. brucei. This DNA damage tolerance may facilitate the generation of virulence-enhancing genetic diversity, within subtelomeric domains in particular. Stringent checkpoints may be similarly lacking in some other eukaryotic cells. IMPORTANCE Chromosome damage must be repaired to prevent the proliferation of defective cells. Alternatively, cells with damage must be eliminated. This is true of human and several other cell types but may not be the case for single-celled parasites, such as trypanosomes. African trypanosomes, which cause lethal diseases in both humans and livestock, can actually exploit chromosomal damage to activate new surface coat proteins and to evade host immune responses, for example. We monitored responses to single chromosomal breaks in trypanosomes using a DNA-binding protein that, in response to DNA damage, forms nuclear foci visible using a microscope. Surprisingly, and unlike what is seen in mammalian cells, these foci persist while cells continue to divide. We also demonstrate chromosome replication even when one chromosome is broken. These results reveal a remarkable degree of damage tolerance in trypanosomes, which may suit the lifestyle of a single-celled parasite, potentially facilitating adaptation and enhancing virulence.
format	article
author	Lucy Glover Catarina A. Marques Olga Suska David Horn
author_facet	Lucy Glover Catarina A. Marques Olga Suska David Horn
author_sort	Lucy Glover
title	Persistent DNA Damage Foci and DNA Replication with a Broken Chromosome in the African Trypanosome
title_short	Persistent DNA Damage Foci and DNA Replication with a Broken Chromosome in the African Trypanosome
title_full	Persistent DNA Damage Foci and DNA Replication with a Broken Chromosome in the African Trypanosome
title_fullStr	Persistent DNA Damage Foci and DNA Replication with a Broken Chromosome in the African Trypanosome
title_full_unstemmed	Persistent DNA Damage Foci and DNA Replication with a Broken Chromosome in the African Trypanosome
title_sort	persistent dna damage foci and dna replication with a broken chromosome in the african trypanosome
publisher	American Society for Microbiology
publishDate	2019
url	https://doaj.org/article/143e3366d41c43898cd4efaedcc625dd
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Persistent DNA Damage Foci and DNA Replication with a Broken Chromosome in the African Trypanosome

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