Modulation of DNA Damage and DNA Repair in Chromatin

Smerdon, Michael J.; Conconi, Antonio

doi:10.1016/s0079-6603(08)60509-7

Cited by 115 publications

(106 citation statements)

References 123 publications

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“…Nucleosomal DNA with an inward rotational setting is likely protected from UV damage as a result of constraints on DNA bending and flexibility imposed by the nucleosome structure (22). Formation of CPDs in DNA depends not only on the absorption of UV photons, but also the flexibility and bending of adjacent pyrimidine bases to allow the photo-induced [2 + 2] cycloaddition reaction to occur (26,27). At inward rotational settings in the nucleosome, the decrease of DNA flexibility and compression of the minor groove is likely responsible for suppressing CPD formation at such sites (27).…”

Section: Discussionmentioning

confidence: 99%

Chromosomal landscape of UV damage formation and repair at single-nucleotide resolution

Mao

Smerdon

Roberts

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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140

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UV-induced DNA lesions are important contributors to mutagenesis and cancer, but it is not fully understood how the chromosomal landscape influences UV lesion formation and repair. Genome-wide profiling of repair activity in UV irradiated cells has revealed significant variations in repair kinetics across the genome, not only among large chromatin domains, but also at individual transcription factor binding sites. Here we report that there is also a striking but predictable variation in initial UV damage levels across a eukaryotic genome. We used a new high-throughput sequencing method, known as CPD-seq, to precisely map UV-induced cyclobutane pyrimidine dimers (CPDs) at single-nucleotide resolution throughout the yeast genome. This analysis revealed that individual nucleosomes significantly alter CPD formation, protecting nucleosomal DNA with an inward rotational setting, even though such DNA is, on average, more intrinsically prone to form CPD lesions. CPD formation is also inhibited by DNAbound transcription factors, in effect shielding important DNA elements from UV damage. Analysis of CPD repair revealed that initial differences in CPD damage formation often persist, even at later repair time points. Furthermore, our high-resolution data demonstrate, to our knowledge for the first time, that CPD repair is significantly less efficient at translational positions near the dyad of strongly positioned nucleosomes in the yeast genome. These findings define the global roles of nucleosomes and transcription factors in both UV damage formation and repair, and have important implications for our understanding of UV-induced mutagenesis in human cancers.DNA repair | DNA damage | nucleosome | chromatin | transcription factor U ltraviolet (UV) light causes extensive damage to DNA by inducing the formation of cyclobutane pyrimidine dimers (CPDs) and, to a lesser extent, 6-4 pyrimidine-pyrimidone photoproducts (6-4PPs). If unrepaired, these DNA lesions block normal DNA replication and are major contributors to mutagenesis in skin cancers (1). CPDs and 6-4PPs are primarily repaired in cells by the nucleotide excision repair (NER) pathway (1). CPD lesions in actively transcribed strands (TS) of DNA are repaired rapidly by the transcription coupled-NER (TC-NER) branch of this repair pathway, which is triggered by RNA polymerase II stalling at UV damage (2, 3). In contrast, CPD lesions in the remainder of the genome are repaired by the global genome NER (GG-NER) subpathway. Differences in repair rates between transcribed and nontranscribed DNA, and between accessible and inaccessible chromatin domains, have been invoked to explain the mutational heterogeneity in many cancer genomes (4-6). To gain new insight into the mutational processes that lead to human cancer, however, a more detailed understanding is needed of the complex interplay of UV damage formation and repair across the genome.Our understanding of how NER operates in different sequence and chromatin contexts has been aided by two recent genome-wide surveys of NER ac...

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Section: Discussionmentioning

confidence: 99%

Chromosomal landscape of UV damage formation and repair at single-nucleotide resolution

Mao

Smerdon

Roberts

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

140

236

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“…Because chromatin rearrangements occur during DNA repair (53,54), the accessibility of EcoRI to rDNA chromatin was followed during NER (Figs. 5 and 6).…”

Section: Discussionmentioning

confidence: 99%

Transcription-coupled repair in RNA polymerase I-transcribed genes of yeast

Conconi

Bespalov

Smerdon

2002

Proc. Natl. Acad. Sci. U.S.A.

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Nucleotide excision repair (NER) of UV-induced cyclobutane pyrimidine dimers (CPDs) was measured in the individual strands of transcriptionally active and inactive ribosomal genes of yeast. Ribosomal genes (rDNA) are present in multiple copies, but only a fraction of them is actively transcribed. Restriction enzyme digestion was used to specifically release the transcriptionally active fraction from yeast nuclei, and selective psoralen crosslinking was used to distinguish between active and inactive rDNA chromatin. Removal of CPDs was followed in both rDNA populations, and the data clearly show that strand-specific repair occurs in transcriptionally active rDNA while being absent in the inactive rDNA fraction. Thus, transcription-coupled repair occurs in RNA polymerase I-transcribed genes in yeast. Moreover, the nontranscribed strand of active rDNA is repaired faster than either strand of inactive rDNA, implying that NER has preferred access to the active, non-nucleosomal rDNA chromatin. Finally, restriction enzyme accessibility to active rDNA varies during NER, suggesting that there is a change in ribosomal gene chromatin structure during or soon after CPD removal. N ucleotide excision repair (NER) removes different types of lesions from DNA, including bulky adducts caused by chemicals, interstrand or intrastrand crosslinks, and the UV photoproducts cis-syn cyclobutane pyrimidine dimer (CPD) and pyrimidine (6-4) pyrimidone (1). If DNA lesions are not removed, mutations can occur after translesion replication (2). It is now well established that many transcriptionally active genes are repaired faster than inactive DNA (3, 4). Furthermore, preferential removal of CPDs from active genes is caused mainly by an increased rate of repair of the transcribed strand (TS). This transcription-coupled repair (TCR) was first discovered in mammalian cells (5), then in Escherichia coli (6) and yeast (7). Elongation by RNA polymerase II (pol II) is required for TCR (8, 9), and it is thought that only pol II-transcribed genes are subject to TCR (10).RNA polymerase I (pol I) transcribes ribosomal genes (rDNA) at a very high rate. The rDNA is localized in the nucleolus, which is a dense chromatin region composed of rDNA, pol I, rRNA, assembling ribosomes, and proteins involved in cell-cycle regulation (11,12). It is known that mammalian cells repair rDNA damaged by UV radiation (13) and chemicals (14-16). However, in rodent and human cells, CPDs are less efficiently repaired in rDNA than in either total genomic DNA or pol II-transcribed genes (16)(17)(18)(19)(20). Moreover, DNA repair does not exhibit strand bias in the rDNA of these cells (17,19). To the contrary, CPDs are rapidly removed from both strands of total rDNA in yeast (21,22). In addition, a strand bias during repair of total rDNA was observed in rad7 and rad16 mutants, even though strand-specific repair was not observed in total rDNA of wild-type cells (21).Ribosomal genes are present in multiple copies organized in long tandem repeats (11), and in most cells only a f...

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“…Changes in chromatin structure are known to go along with NER and are required for efficient DNA repair in the context of condensed chromatin [79,80]. Recent studies in yeast revealed an enhanced association of subunits of the SWI/SNF chromatin-remodelling complex with Rad4-Rad23 (XPC-RAD23B in human), the principal DNA damage recognition factor in GG-NER [81].…”

Section: Recruitment Of Chromatin Remodellers In Tc-nermentioning

confidence: 99%

Transcription-coupled nucleotide excision repair in mammalian cells: molecular mechanisms and biological effects

2008

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The encounter of elongating RNA polymerase II (RNAPIIo) with DNA lesions has severe consequences for the cell as this event provides a strong signal for P53-dependent apoptosis and cell cycle arrest. To counteract prolonged blockage of transcription, the cell removes the RNAPIIo-blocking DNA lesions by transcription-coupled repair (TC-NER), a specialized subpathway of nucleotide excision repair (NER). Exposure of mice to UVB light or chemicals has elucidated that TC-NER is a critical survival pathway protecting against acute toxic and long-term effects (cancer) of genotoxic exposure. Deficiency in TC-NER is associated with mutations in the CSA and CSB genes giving rise to the rare human disorder Cockayne syndrome (CS). Recent data suggest that CSA and CSB play differential roles in mammalian TC-NER: CSB as a repair coupling factor to attract NER proteins, chromatin remodellers and the CSA-E3-ubiquitin ligase complex to the stalled RNAPIIo. CSA is dispensable for attraction of NER proteins, yet in cooperation with CSB is required to recruit XAB2, the nucleosomal binding protein HMGN1 and TFIIS. The emerging picture of TC-NER is complex: repair of transcription-blocking lesions occurs without displacement of the DNA damage-stalled RNAPIIo, and requires at least two essential assembly factors (CSA and CSB), the core NER factors (except for XPC-RAD23B), and TC-NER specific factors. These and yet unidentified proteins will accomplish not only efficient repair of transcription-blocking lesions, but are also likely to contribute to DNA damage signalling events.

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Modulation of DNA Damage and DNA Repair in Chromatin

Cited by 115 publications

References 123 publications

Chromosomal landscape of UV damage formation and repair at single-nucleotide resolution

Chromosomal landscape of UV damage formation and repair at single-nucleotide resolution

Transcription-coupled repair in RNA polymerase I-transcribed genes of yeast

Transcription-coupled nucleotide excision repair in mammalian cells: molecular mechanisms and biological effects

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