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...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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American Society for Microbiology
2019-08-01
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| Series: | mBio |
| Subjects: | |
| Online Access: | https://journals.asm.org/doi/10.1128/mBio.01252-19 |
| _version_ | 1819199775108497408 |
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| 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 |
| collection | DOAJ |
| 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. |
| first_indexed | 2024-12-23T03:21:41Z |
| format | Article |
| id | doaj.art-143e3366d41c43898cd4efaedcc625dd |
| institution | Directory Open Access Journal |
| issn | 2150-7511 |
| language | English |
| last_indexed | 2024-12-23T03:21:41Z |
| publishDate | 2019-08-01 |
| publisher | American Society for Microbiology |
| record_format | Article |
| series | mBio |
| spelling | doaj.art-143e3366d41c43898cd4efaedcc625dd2022-12-21T18:01:59ZengAmerican Society for MicrobiologymBio2150-75112019-08-0110410.1128/mBio.01252-19Persistent DNA Damage Foci and DNA Replication with a Broken Chromosome in the African TrypanosomeLucy Glover0Catarina A. Marques1Olga Suska2David Horn3Wellcome Trust Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dundee, United KingdomWellcome Trust Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dundee, United KingdomWellcome Trust Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dundee, United KingdomWellcome Trust Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dundee, United KingdomABSTRACT 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.https://journals.asm.org/doi/10.1128/mBio.01252-19RPA2damage responsetelomere |
| spellingShingle | Lucy Glover Catarina A. Marques Olga Suska David Horn Persistent DNA Damage Foci and DNA Replication with a Broken Chromosome in the African Trypanosome mBio RPA2 damage response telomere |
| title | 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_short | 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 |
| topic | RPA2 damage response telomere |
| url | https://journals.asm.org/doi/10.1128/mBio.01252-19 |
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