Identification of the DNA sequence from the E. coli terminus region that halts replication forks

Hill, Thomas M.; Pelletier, Anthony J.; Tecklenburg, Marianne; Kuempel, Peter L.

doi:10.1016/0092-8674(88)90032-3

Cited by 131 publications

(116 citation statements)

References 26 publications

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“…From this point of view, it is very interesting that condensin in human cells is concentrated in the nucleolus during the interphase (8). Further, in bacteria, both SMC-like proteins (e.g., that encoded by mukB in Escherichia coli) and replication fork blocking systems (Ter site and Tus protein) are found, and chromosome segregation defects were observed in mutants of SMC-related genes (6,19,21,22,37,39,53). Therefore, the relationship between replication forks converging at specific sites and condensin association may be important not only for repeat but also for nonrepeat regions.…”

Section: Discussionmentioning

confidence: 99%

Condensin Loaded onto the Replication Fork Barrier Site in the rRNA Gene Repeats during S Phase in a FOB1-Dependent Fashion To Prevent Contraction of a Long Repetitive Array in Saccharomyces cerevisiae

Johzuka

Terasawa

Ogawa

et al. 2006

Molecular and Cellular Biology

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An average of 200 copies of the rRNA gene (rDNA) is clustered in a long tandem array in Saccharomyces cerevisiae. FOB1 is known to be required for expansion/contraction of the repeats by stimulating recombination, thereby contributing to the maintenance of the average copy number. In ⌬fob1 cells, the repeats are still maintained without any fluctuation in the copy number, suggesting that another, unknown system acts to prevent repeat contraction. Here, we show that condensin acts together with FOB1 in a functionally complemented fashion to maintain the long tandem repeats. Six condensin mutants possessing severely contracted rDNA repeats were isolated in ⌬fob1 cells but not in FOB1 ؉ cells. We also found that the condensin complex associated with the nontranscribed spacer region of rDNA with a major peak coincided with the replication fork barrier (RFB) site in a FOB1-dependent fashion. Surprisingly, condensin association with the RFB site was established during S phase and was maintained until anaphase. These results indicate that FOB1 plays a novel role in preventing repeat contraction by regulating condensin association and suggest a link between replication termination and chromosome condensation and segregation.Repeated sequences and genes are extensively distributed throughout the genomes of many organisms. A common feature of these repeats is instability; the copy number of repeats frequently fluctuates, and they are exposed to the risk of contraction. However, the mechanisms responsible for the fluctuation of repeat copy number and for the maintenance of the repeats remain largely unknown. The eukaryotic rRNA gene (rDNA) family is a typical repeated structure. The genes are generally clustered in long tandem repeats on one or several loci in most eukaryote genomes. In the yeast Saccharomyces cerevisiae, 200 copies on average are tandemly arrayed in a central position on the longest chromosome, chromosome XII. A single rDNA unit (9.1 kb) comprises a 35S rRNA coding region which is transcribed by RNA polymerase I, the 5S rRNA coding region transcribed by RNA polymerase III, and two nontranscribed spacers (NTS), i.e., NTS1 and NTS2 (see Fig. 5A). The replication origin (ARS) and the replication fork barrier (RFB) are located within NTS2 and NTS1, respectively (5, 33, 42). The whole length of the tandem array extends ϳ1.9 Mb.One system that maintains the average copy number of the rDNA long tandem array has been reported in recent years. High frequencies of recombination events and expansion/contraction of the repeats are observed for FOB1 ϩ strains, whereas deletion of FOB1 (⌬fob1) eliminates both events (14,24,27). Furthermore, DNA strand break formation around the RFB site was observed to be FOB1 dependent (7,29,47). FOB1 is therefore thought to be required for the maintenance of average copy number by increasing or decreasing copy number through the regulation of recombination events between the repeats. In ⌬fob1 cells, surprisingly, the rDNA tandem array is still maintained stably without any expansion/...

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Section: Discussionmentioning

confidence: 99%

Condensin Loaded onto the Replication Fork Barrier Site in the rRNA Gene Repeats during S Phase in a FOB1-Dependent Fashion To Prevent Contraction of a Long Repetitive Array in Saccharomyces cerevisiae

Johzuka

Terasawa

Ogawa

et al. 2006

Molecular and Cellular Biology

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“…Competent cells were transformed with monomeric forms of pBR-terE@StyI, pBRterE@AatII, or pBR-terE@DraI and all derivatives of pBR322 with the polar replication terminator TerE (31,32) cloned at variable distances from the unidirectional ColE1 origin as described before (29). DH5␣FЈ cells were grown in LB medium at 37°C, and parE10 cells were grown at the restrictive temperature (43°C).…”

Section: Methodsmentioning

confidence: 99%

“…In an attempt to shed new light on this issue, we used classical genetics and high resolution two-dimensional agarose gel electrophoresis to examine the RIs of the following three bacterial plasmids, pBR-terE@StyI, pBR-terE@AatII, and pBR-terE@DraI (29), isolated from E. coli strains with different combinations of topoisomerases. In most cases for these three plasmids, the replicating fork stalls as it reaches the TerE-Tus complex (31,32). This blockage leads to the accumulation of partially replicated molecules with a mass ϳ1.2ϫ, ϳ1.6ϫ, and ϳ1.8ϫ the mass of unreplicated molecules (Fig.…”

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confidence: 99%

Direct Evidence for the Formation of Precatenanes during DNA Replication

Cebrián

Castán

López‐Martínez

et al. 2015

Journal of Biological Chemistry

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Background: Changes in DNA topology during replication are still poorly understood. Results: Classical genetics and two-dimensional agarose gel electrophoresis showed that RIs tensioned in the absence of Topo IV. Conclusion:The results indicated that replication forks swivel in vivo leading to the formation of precatenanes as replication progresses. Significance: This conclusion ends a long lasting debate on the formation of precatenanes during replication.

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“…To investigate the role of replication fork pausing as a possible elicitor of dif activity, psrA has been removed by a 15-kb deletion to yield strain LN3167. This strain is Dif + (Table 3), as are strains having undergone deletions of the tus locus Idata not shown}, which controls site-specific replication pausing (Hill et al 1988;Khatri et al 1989;Lee et al 1989}. In strain LN3034 , the region where replication termi- Table 2.…”

Section: Dif Activity Does Not Require Termination Of Replication In mentioning

confidence: 99%

Restriction of the activity of the recombination site dif to a small zone of the Escherichia coli chromosome.

Cornet¹,

Patte²,

Louarn³

1996

Genes Dev.

126

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The recombination site dif is the target on the Escherichia coli chromosome of the site-specific recombinases XerC and XerD. The dif/XerC-D system plays a role during the cell cycle, probably by favoring sister chromosome monomerization or separation. A phenomenon of regional control over dif activity, also analyzed in this issue, is demonstrated here by translocation of dif to a series of loci close to the normal locus. We found that the site is physiologically active only within a narrow zone around its natural position.Competence for dif activity does not depend on the sequence of the normal dif activity zone (DAZ), because ~(diD deletions larger than the DAZ result in Dif + bacteria when dif is reinserted at the junction point. Although dif maps where replication normally terminates, termination of replication is not the elicitor. A strain with a large inversion that places dif and its surrounding region close to oriC remains Dif*, even when a Tus-mutation allows replication to terminate far away from it. Preliminary data suggest the possibility that specialized sequences separate the competent zone from the rest of the chromosome. We suspect that these sequences are members of a set of sequences involved in a polarized process of postreplicative reconstruction of the nucleoid structure. We propose that this reconstruction forces catenation links between sister chromosomes to accumulate within the DAZ, where they eventually favor recombination at d/f.[Key Words." Site-specific recombination; dif site domain of activity; E. coli chromosome organization] Received January 10, 1996; revised version accepted March 20, 1996.The

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Identification of the DNA sequence from the E. coli terminus region that halts replication forks

Cited by 131 publications

References 26 publications

Condensin Loaded onto the Replication Fork Barrier Site in the rRNA Gene Repeats during S Phase in a FOB1-Dependent Fashion To Prevent Contraction of a Long Repetitive Array in Saccharomyces cerevisiae

Condensin Loaded onto the Replication Fork Barrier Site in the rRNA Gene Repeats during S Phase in a FOB1-Dependent Fashion To Prevent Contraction of a Long Repetitive Array in Saccharomyces cerevisiae

Direct Evidence for the Formation of Precatenanes during DNA Replication

Restriction of the activity of the recombination site dif to a small zone of the Escherichia coli chromosome.

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