Interference Between DNA Replication and Transcription as a Cause of Genomic Instability

Lin, Yea-Lih; Pasero, Philippe

doi:10.2174/138920212799034767

Cited by 56 publications

(44 citation statements)

References 110 publications

(137 reference statements)

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“…4). In eukaryotes, PFA is required for (i) prevention of collision between a replication fork and an actively transcribing RNA polymerase approaching from the opposite direction, thereby preventing genome instability (30)(31)(32)(33), (ii) promoting genetic imprinting and cellular differentiation in fission yeast (12), and (iii) controlling replicative life span in budding yeast (34,35).…”

Section: Significancementioning

confidence: 99%

Phosphorylation of CMG helicase and Tof1 is required for programmed fork arrest

Bastia

Srivastava

Zaman

et al. 2016

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

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Several important physiological transactions, including control of replicative life span (RLS), prevention of collision between replication and transcription, and cellular differentiation, require programmed replication fork arrest (PFA). However, a general mechanism of PFA has remained elusive. We previously showed that the Tof1–Csm3 fork protection complex is essential for PFA by antagonizing the Rrm3 helicase that displaces nonhistone protein barriers that impede fork progression. Here we show that mutations of Dbf4-dependent kinase (DDK) of Saccharomyces cerevisiae, but not other DNA replication factors, greatly reduced PFA at replication fork barriers in the spacer regions of the ribosomal DNA array. A key target of DDK is the mini chromosome maintenance (Mcm) 2–7 complex, which is known to require phosphorylation by DDK to form an active CMG [Cdc45 (cell division cycle gene 45), Mcm2–7, GINS (Go, Ichi, Ni, and San)] helicase. In vivo experiments showed that mutational inactivation of DDK caused release of Tof1 from the chromatin fractions. In vitro binding experiments confirmed that CMG and/or Mcm2–7 had to be phosphorylated for binding to phospho-Tof1–Csm3 but not to its dephosphorylated form. Suppressor mutations that bypass the requirement for Mcm2–7 phosphorylation by DDK restored PFA in the absence of the kinase. Retention of Tof1 in the chromatin fraction and PFA in vivo was promoted by the suppressor mcm5-bob1, which bypassed DDK requirement, indicating that under this condition a kinase other than DDK catalyzed the phosphorylation of Tof1. We propose that phosphorylation regulates the recruitment and retention of Tof1–Csm3 by the replisome and that this complex antagonizes the Rrm3 helicase, thereby promoting PFA, by preserving the integrity of the Fob1–Ter complex.

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Section: Significancementioning

confidence: 99%

Phosphorylation of CMG helicase and Tof1 is required for programmed fork arrest

Bastia

Srivastava

Zaman

et al. 2016

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

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“…In either case, encounters between the two machineries can result in replication stress (7,8). However, expression from the lagging strand is thought to be disfavored, because it can lead to increased replication stalling, replication restart, and genomic instability compared with codirectionally oriented genes (7,(9)(10)(11). Although head-on transcription is demonstrably more detrimental to the cell, the fundamental mechanism that underlies orientationdependent severity remains a mystery.…”

mentioning

confidence: 99%

An underlying mechanism for the increased mutagenesis of lagging-strand genes in Bacillus subtilis

Million-Weaver¹,

Samadpour²,

Moreno-Habel³

et al. 2015

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

128

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We previously reported that lagging-strand genes accumulate mutations faster than those encoded on the leading strand in Bacillus subtilis. Although we proposed that orientation-specific encounters between replication and transcription underlie this phenomenon, the mechanism leading to the increased mutagenesis of lagging-strand genes remained unknown. Here, we report that the transcription-dependent and orientation-specific differences in mutation rates of genes require the B. subtilis Y-family polymerase, PolY1 (yqjH). We find that without PolY1, association of the replicative helicase, DnaC, and the recombination protein, RecA, with lagging-strand genes increases in a transcription-dependent manner. These data suggest that PolY1 promotes efficient replisome progression through lagging-strand genes, thereby reducing potentially detrimental breaks and single-stranded DNA at these loci. Y-family polymerases can alleviate potential obstacles to replisome progression by facilitating DNA lesion bypass, extension of D-loops, or excision repair. We find that the nucleotide excision repair (NER) proteins UvrA, UvrB, and UvrC, but not RecA, are required for transcription-dependent asymmetry in mutation rates of genes in the two orientations. Furthermore, we find that the transcription-coupling repair factor Mfd functions in the same pathway as PolY1 and is also required for increased mutagenesis of laggingstrand genes. Experimental and SNP analyses of B. subtilis genomes show mutational footprints consistent with these findings. We propose that the interplay between replication and transcription increases lesion susceptibility of, specifically, lagging-strand genes, activating an Mfd-dependent error-prone NER mechanism. We propose that this process, at least partially, underlies the accelerated evolution of lagging-strand genes.replication conflicts | transcription orientation | Y-family polymerases | excision repair | TCR

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“…Transcription frequently impedes replication in bacteria, necessitating numerous factors to resolve conflicts between the two machineries (5). Head-on collisions between replication and transcription, which occur when a gene is carried on the lagging strand, cause mutagenesis, genomic instability, single-stranded DNA (ssDNA) accumulation, and potentially double-strand DNA breaks (6)(7)(8)(9).…”

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confidence: 99%

Replication Restart after Replication-Transcription Conflicts Requires RecA in Bacillus subtilis

2015

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Efficient duplication of genomes depends on reactivation of replication forks outside the origin. Replication restart can be facilitated by recombination proteins, especially if single-or double-strand breaks form in the DNA. Each type of DNA break is processed by a distinct pathway, though both depend on the RecA protein. One common obstacle that can stall forks, potentially leading to breaks in the DNA, is transcription. Though replication stalling by transcription is prevalent, the nature of DNA breaks and the prerequisites for replication restart in response to these encounters remain unknown. Here, we used an engineered site-specific replication-transcription conflict to identify and dissect the pathways required for the resolution and restart of replication forks stalled by transcription in Bacillus subtilis. We found that RecA, its loader proteins RecO and AddAB, and the Holliday junction resolvase RecU are required for efficient survival and replication restart after conflicts with transcription. Genetic analyses showed that RecO and AddAB act in parallel to facilitate RecA loading at the site of the conflict but that they can each partially compensate for the other's absence. Finally, we found that RecA and either RecO or AddAB are required for the replication restart and helicase loader protein, DnaD, to associate with the engineered conflict region. These results suggest that conflicts can lead to both single-strand gaps and double-strand breaks in the DNA and that RecA loading and Holliday junction resolution are required for replication restart at regions of replication-transcription conflicts. IMPORTANCEHead-on conflicts between replication and transcription occur when a gene is expressed from the lagging strand. These encounters stall the replisome and potentially break the DNA. We investigated the necessary mechanisms for Bacillus subtilis cells to overcome a site-specific engineered conflict with transcription of a protein-coding gene. We found that the recombination proteins RecO and AddAB both load RecA onto the DNA in response to the head-on conflict. Additionally, RecA loading by one of the two pathways was required for both replication restart and efficient survival of the collision. Our findings suggest that both single-strand gaps and double-strand DNA breaks occur at head-on conflict regions and demonstrate a requirement for recombination to restart replication after collisions with transcription.

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Interference Between DNA Replication and Transcription as a Cause of Genomic Instability

Cited by 56 publications

References 110 publications

Phosphorylation of CMG helicase and Tof1 is required for programmed fork arrest

Phosphorylation of CMG helicase and Tof1 is required for programmed fork arrest

An underlying mechanism for the increased mutagenesis of lagging-strand genes in Bacillus subtilis

Replication Restart after Replication-Transcription Conflicts Requires RecA in Bacillus subtilis

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