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An essential role for the DNA breakage-repair protein Ku80 in programmed DNA rearrangements in Tetrahymena thermophila

Programmed DNA rearrangements are important processes present in many organisms. In the ciliated protozoan Tetrahymena thermophila, DNA rearrangements occur during the sexual conjugation process and lead to the deletion of thousands of specific DNA segments and fragmentation of the chromosomes. In t...

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Autores principales: Lin, I-Ting, Chao, Ju-Lan, Yao, Meng-Chao
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The American Society for Cell Biology 2012
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3364183/
https://www.ncbi.nlm.nih.gov/pubmed/22513090
http://dx.doi.org/10.1091/mbc.E11-11-0952
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author Lin, I-Ting
Chao, Ju-Lan
Yao, Meng-Chao
author_facet Lin, I-Ting
Chao, Ju-Lan
Yao, Meng-Chao
author_sort Lin, I-Ting
collection PubMed
description Programmed DNA rearrangements are important processes present in many organisms. In the ciliated protozoan Tetrahymena thermophila, DNA rearrangements occur during the sexual conjugation process and lead to the deletion of thousands of specific DNA segments and fragmentation of the chromosomes. In this study, we found that the Ku80 homologue, a conserved component of the nonhomologous end-joining process of DNA repair, was essential for these two processes. During conjugation, TKU80 was highly expressed and localized to the new macronucleus, where DNA rearrangements occur. Homokaryon TKU80-knockout mutants are unable to complete conjugation and produce progeny and are arrested at the two-micronuclei/two-macronuclei stage. Analysis of their DNA revealed failure to complete DNA deletion. However, the DNA-cutting step appeared to have occurred, as evidenced by the presence of circularized excised DNA. Moreover, chromosome breakage or de novo telomere addition was affected. The mutant appears to accumulate free DNA ends detectable by terminal deoxynucleotidyl transferase dUTP nick end labeling assays that led to the degradation of most DNA in the developing macronucleus. These findings suggest that Tku80p may serve an end-protective role after DNA cleavage has occurred. Unexpectedly, the large heterochromatin structures that normally associate with DNA rearrangements failed to form without TKU80. Together the results suggest multiple roles for Tku80p and indicate that a Ku-dependent DNA-repair pathway is involved in programmed DNA rearrangements in Tetrahymena.
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spelling pubmed-33641832012-08-16 An essential role for the DNA breakage-repair protein Ku80 in programmed DNA rearrangements in Tetrahymena thermophila Lin, I-Ting Chao, Ju-Lan Yao, Meng-Chao Mol Biol Cell Articles Programmed DNA rearrangements are important processes present in many organisms. In the ciliated protozoan Tetrahymena thermophila, DNA rearrangements occur during the sexual conjugation process and lead to the deletion of thousands of specific DNA segments and fragmentation of the chromosomes. In this study, we found that the Ku80 homologue, a conserved component of the nonhomologous end-joining process of DNA repair, was essential for these two processes. During conjugation, TKU80 was highly expressed and localized to the new macronucleus, where DNA rearrangements occur. Homokaryon TKU80-knockout mutants are unable to complete conjugation and produce progeny and are arrested at the two-micronuclei/two-macronuclei stage. Analysis of their DNA revealed failure to complete DNA deletion. However, the DNA-cutting step appeared to have occurred, as evidenced by the presence of circularized excised DNA. Moreover, chromosome breakage or de novo telomere addition was affected. The mutant appears to accumulate free DNA ends detectable by terminal deoxynucleotidyl transferase dUTP nick end labeling assays that led to the degradation of most DNA in the developing macronucleus. These findings suggest that Tku80p may serve an end-protective role after DNA cleavage has occurred. Unexpectedly, the large heterochromatin structures that normally associate with DNA rearrangements failed to form without TKU80. Together the results suggest multiple roles for Tku80p and indicate that a Ku-dependent DNA-repair pathway is involved in programmed DNA rearrangements in Tetrahymena. The American Society for Cell Biology 2012-06-01 /pmc/articles/PMC3364183/ /pubmed/22513090 http://dx.doi.org/10.1091/mbc.E11-11-0952 Text en © 2012 Lin et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0). “ASCB®,” “The American Society for Cell Biology®,” and “Molecular Biology of the Cell®” are registered trademarks of The American Society of Cell Biology.
spellingShingle Articles
Lin, I-Ting
Chao, Ju-Lan
Yao, Meng-Chao
An essential role for the DNA breakage-repair protein Ku80 in programmed DNA rearrangements in Tetrahymena thermophila
title An essential role for the DNA breakage-repair protein Ku80 in programmed DNA rearrangements in Tetrahymena thermophila
title_full An essential role for the DNA breakage-repair protein Ku80 in programmed DNA rearrangements in Tetrahymena thermophila
title_fullStr An essential role for the DNA breakage-repair protein Ku80 in programmed DNA rearrangements in Tetrahymena thermophila
title_full_unstemmed An essential role for the DNA breakage-repair protein Ku80 in programmed DNA rearrangements in Tetrahymena thermophila
title_short An essential role for the DNA breakage-repair protein Ku80 in programmed DNA rearrangements in Tetrahymena thermophila
title_sort essential role for the dna breakage-repair protein ku80 in programmed dna rearrangements in tetrahymena thermophila
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3364183/
https://www.ncbi.nlm.nih.gov/pubmed/22513090
http://dx.doi.org/10.1091/mbc.E11-11-0952
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