Suppressors of transcriptional transgenic silencing in Chlamydomonas are sensitive to DNA-damaging agents and reactivate transposable elements

Byeong Ryool Jeong, Dancia Wu-Scharf, Chaomei Zhang, Heriberto Cerutti

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58 Citations (Scopus)

Abstract

In the unicellular green alga Chlamydomonas reinhardtii, the epigenetic silencing of transgenes occurs, as in land plants, at both the transcriptional and posttranscriptional levels. In the case of single-copy transgenes, transcriptional silencing takes place without detectable cytosine methylation of the introduced DNA. We have isolated two mutant strains, Mut-9 and Mut-11, that reactivate expression of a transcriptionally silenced single-copy transgene. These suppressors are deficient in the repression of a DNA transposon and a retrotransposon-like element. In addition, the mutants show enhanced sensitivity to DNA-damaging agents, particularly radiomimetic chemicals inducing DNA double-strand breaks. All of these phenotypes are much more prominent in a double mutant strain. These observations suggest that multiple partly redundant epigenetic mechanisms are involved in the repression of transgenes and transposons in eukaryotes, presumably as components of a system that evolved to preserve genomic stability. Our results also raise the possibility of mechanistic connections between epigenetic transcriptional silencing and DNA double-strand break repair.

Original languageEnglish (US)
Pages (from-to)1076-1081
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume99
Issue number2
DOIs
StatePublished - Jan 22 2002

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Chlamydomonas
DNA Transposable Elements
Transgenes
Epigenomics
Double-Stranded DNA Breaks
DNA
Embryophyta
Chlamydomonas reinhardtii
Retroelements
Chlorophyta
Genomic Instability
Cytosine
DNA Methylation
Eukaryota
Phenotype

ASJC Scopus subject areas

  • General

Cite this

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abstract = "In the unicellular green alga Chlamydomonas reinhardtii, the epigenetic silencing of transgenes occurs, as in land plants, at both the transcriptional and posttranscriptional levels. In the case of single-copy transgenes, transcriptional silencing takes place without detectable cytosine methylation of the introduced DNA. We have isolated two mutant strains, Mut-9 and Mut-11, that reactivate expression of a transcriptionally silenced single-copy transgene. These suppressors are deficient in the repression of a DNA transposon and a retrotransposon-like element. In addition, the mutants show enhanced sensitivity to DNA-damaging agents, particularly radiomimetic chemicals inducing DNA double-strand breaks. All of these phenotypes are much more prominent in a double mutant strain. These observations suggest that multiple partly redundant epigenetic mechanisms are involved in the repression of transgenes and transposons in eukaryotes, presumably as components of a system that evolved to preserve genomic stability. Our results also raise the possibility of mechanistic connections between epigenetic transcriptional silencing and DNA double-strand break repair.",
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T1 - Suppressors of transcriptional transgenic silencing in Chlamydomonas are sensitive to DNA-damaging agents and reactivate transposable elements

AU - Jeong, Byeong Ryool

AU - Wu-Scharf, Dancia

AU - Zhang, Chaomei

AU - Cerutti, Heriberto

PY - 2002/1/22

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N2 - In the unicellular green alga Chlamydomonas reinhardtii, the epigenetic silencing of transgenes occurs, as in land plants, at both the transcriptional and posttranscriptional levels. In the case of single-copy transgenes, transcriptional silencing takes place without detectable cytosine methylation of the introduced DNA. We have isolated two mutant strains, Mut-9 and Mut-11, that reactivate expression of a transcriptionally silenced single-copy transgene. These suppressors are deficient in the repression of a DNA transposon and a retrotransposon-like element. In addition, the mutants show enhanced sensitivity to DNA-damaging agents, particularly radiomimetic chemicals inducing DNA double-strand breaks. All of these phenotypes are much more prominent in a double mutant strain. These observations suggest that multiple partly redundant epigenetic mechanisms are involved in the repression of transgenes and transposons in eukaryotes, presumably as components of a system that evolved to preserve genomic stability. Our results also raise the possibility of mechanistic connections between epigenetic transcriptional silencing and DNA double-strand break repair.

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