Mechanism of phage Mu-1 integration: nalidixic acid treatment causes clustering of Mu-1-induced mutations near replication origin.

Paolozzi, L.; Jucker, Richard; Calef, E.

doi:10.1073/pnas.75.10.4940

Cited by 14 publications

(15 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Tap protein regulates initiation frequency, with individual rep genes playing roles in replisome assembly and priming of DNA synthesis in both clockwise and counterclockwise directions. Early work suggested that Mu inserts preferentially near replication forks (Paolozzi et al, 1978;Fitts and Taylor, 1980). Later studies weighed against a preestablished replication fork bias (Nakai and Taylor, 1985;Sivan et al, 1988).…”

Section: A Pslt Hot Spot Linked To Dna Replicationmentioning

confidence: 99%

Microarray analysis of Mu transposition in Salmonella enterica, serovar Typhimurium: transposon exclusion by high‐density DNA binding proteins

Manna

Porwollik

McClelland

et al. 2007

Molecular Microbiology

View full text Add to dashboard Cite

SummaryAll organisms contain transposons with the potential to disrupt and rearrange genes. Despite the presence of these destabilizing sequences, some genomes show remarkable stability over evolutionary time. Do bacteria defend the genome against disruption by transposons? Phage Mu replicates by transposition and virtually all genes are potential insertion targets. To test whether bacteria limit Mu transposition to specific parts of the chromosome, DNA arrays of Salmonella enterica were used to quantitatively measure target site preference and compare the data with Escherichia coli. Essential genes were as susceptible to transposon disruption as non-essential ones in both organisms, but the correlation of transposition hot spots among homologous genes was poor. Genes in highly transcribed operons were insulated from transposon mutagenesis in both organisms. A 10 kb cold spot on the pSLT plasmid was near parS, a site to which the ParB protein binds and spreads along DNA. Deleting ParB erased the plasmid cold spot, and an ectopic parS site placed in the Salmonella chromosome created a new cold spot in the presence of ParB. Our data show that competition between cellular proteins and transposition proteins on plasmids and the chromosome is a dominant factor controlling the genetic footprint of transposons in living cells.

show abstract

Section: A Pslt Hot Spot Linked To Dna Replicationmentioning

confidence: 99%

Microarray analysis of Mu transposition in Salmonella enterica, serovar Typhimurium: transposon exclusion by high‐density DNA binding proteins

Manna

Porwollik

McClelland

et al. 2007

Molecular Microbiology

View full text Add to dashboard Cite

show abstract

“…Secondary transpositions to many different sites also occur, as is reflected by the variability of host sequences at both ends of the viral DNA (3,4). The ability of Mu DNA to integrate into many sites led to the hypothesis that it is inserted preferentially at chromosome replication forks (9,21,22). The hypothesis of preference for replication forks for lysogenic integrations was supported by the frequencies of gene inactivation in nalidixic acid-treated cells (22) and by sequential inactivation of genes in synchronized cultures infected at intervals (21).…”

mentioning

confidence: 99%

“…The ability of Mu DNA to integrate into many sites led to the hypothesis that it is inserted preferentially at chromosome replication forks (9,21,22). The hypothesis of preference for replication forks for lysogenic integrations was supported by the frequencies of gene inactivation in nalidixic acid-treated cells (22) and by sequential inactivation of genes in synchronized cultures infected at intervals (21). Comparative kinetics of zygotic induction of synchronized, Mu-infected Hfr strains indicated that in a lytic pathway as well, at least the earlier transpositions occur preferentially at replication forks (9).…”

mentioning

confidence: 99%

Replication forks of Escherichia coli are not the preferred sites for lysogenic integration of bacteriophage Mu

1988

View full text Add to dashboard Cite

The question of whether bacteriophage Mu prefers replication forks for lysogenic integration into Escherichia coli chromosomes was tested by using two different systems. In the first, inactivation of genes was scored in synchronized cultures infected by Mu at various times. No increase in the mutation frequency of a gene was found after infection at the time of its replication. In the second, the composition of colonies formed by bacteria lysogenized by Mu was determined; the newly formed lysogens should give rise to mixed colonies (containing lysogenized as well as nonlysogenized bacteria), uniform colonies, or both, depending on the mode of integration. Both types of colonies were found, and the fraction of uniform colonies was proportional to the relative length of the unreplicated segment of an average chromosome in the culture. The results in both systems clearly preclude the possibility that a lysogenizing Mu integrates with high preference at the chromosome replication forks.Bacteriophage Mu integrates at many different sites upon lysogenization of Escherichia coli cells (5, 24), with a possible preference for certain "hot spots" (8,23). Secondary transpositions to many different sites also occur, as is reflected by the variability of host sequences at both ends of the viral DNA (3, 4). The ability of Mu DNA to integrate into many sites led to the hypothesis that it is inserted preferentially at chromosome replication forks (9,21,22). The hypothesis of preference for replication forks for lysogenic integrations was supported by the frequencies of gene inactivation in nalidixic acid-treated cells (22) and by sequential inactivation of genes in synchronized cultures infected at intervals (21). Comparative kinetics of zygotic induction of synchronized, Mu-infected Hfr strains indicated that in a lytic pathway as well, at least the earlier transpositions occur preferentially at replication forks (9).These results were satisfactory because they were in keeping with the prevailing ideas that Mu exploits nicks or gaps as well as special proteins found in the "replisome" (9) and that replication of Mu DNA is an obvious step for its integration (9). However, it is now generally accepted that each transposon participates in determining the specificity of the staggered cut made at the target (13), thus eliminating the need for existing nicks. Moreover, it has been demonstrated that the first integration of Mu is conservative and does not require previous replication (10, 15). It therefore seems worthwhile to reexamine the hypothesis that the first integration of Mu occurs preferentially at replication forks.Using a sandwich hybridization assay, it has been demonstrated in recent years that chromosome replication forks are not preferred targets for secondary transpositions during lytic development of Mu (19). Moreover, the above-mentioned results of zygotic induction (9) (19). There still exists the possibility of a fundamental difference between the targets of Mu integrations in lysogenic and other transpositions.In...

show abstract

“…Along with earlier observations on transposition from nonreplicating bacteriophage genomes (5), these experiments indicated that replication of donor replicons was not essential for transposable element DNA rearrangements. On the other hand, studies of the specificity of bacteriophage Mu insertion into the E. coli chromosome suggested a particular affinity for the replication fork and, consequently, a possible recombinational role of the target molecule's replication mechanism (6,7). In order to study this possibility further, we examined the effect on Tnl -specific replicative recombination of blocking target replicon duplication.…”

mentioning

confidence: 99%

Recombination involving transposable elements: role of target molecule replication in Tn1 delta Ap-mediated replicon fusion.

Muster¹,

Shapiro²,

MacHattie³

1983

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

View full text Add to dashboard Cite

Donor DNA molecules carrying Tnl or Tn3 deletion mutants do not need to replicate in order to participate in replicon fusion recombination events during which the Tnl/Tn3 element is duplicated. We have assayed Tn1AAp-mediated replicon fusion events involving plasmid R388 and the bacteriophage A-derived plasmid pACM, and we find that the role of the recipient molecule is distinct. When pACM carries Tn1AAp, replicon fusion occurs in more than 1% of all cells assayed, whether or not pACM: :TnlAAp can replicate. In contrast, when R388 carries TnlAAp, replicon fusion occurs only when the pACM target can replicate. Blocks to pACM replication by prophage repressor or amber mutations of the 0 and P cistrons reduce replicon fusion so that it occurs in less than 1 out of 105 cells assayed.Transposable elements in Escherichia coli and other Gram-negative bacteria can mediate recombination between DNA segments that share no genetic homology. The products of recombination are generally observed to contain two duplicated sequences: the transposable element from the "donor" segment and a short oligonucleotide at the "target" segment. The formation of these products is explicable by models that postulate a series of biochemical steps, including replication of the duplicated sequences, as an integral part of the recombination mechanism (1-3). Our earlier results on replicon fusion supported such models by showing that a mutant Tn3 element can undergo duplication in replicative recombination even when it is present in a donor DNA molecule whose normal replication mechanism has been blocked (Fig. 1 Top; ref. 4). Along with earlier observations on transposition from nonreplicating bacteriophage genomes (5), these experiments indicated that replication of donor replicons was not essential for transposable element DNA rearrangements. On the other hand, studies of the specificity of bacteriophage Mu insertion into the E. coli chromosome suggested a particular affinity for the replication fork and, consequently, a possible recombinational role of the target molecule's replication mechanism (6, 7). In order to study this possibility further, we examined the effect on Tnl -specific replicative recombination of blocking target replicon duplication. Our experiments utilized the pACM cosmid/plasmid system (8,9). Deletion of the b2-N interval from a A: :Tn9 genome creates a pACM molecule that can reproduce as a plasmid, dependent on A-specific replication functions encoded by cistrons O and P. or as a virus in cells that contain A N product. The replication of pACM is readily controlled, either by prophage repressor or by mutations of the 0 and P cistrons (9). We have used both methods to prevent pACM replication when it is a donor or a target for replicon fusion ( Fig. 1 Middle and Bottom). Our data indicate that more than 99.9% of TnlAAp-mediated recombination events depend on active replication of the target molecule but not of the donor molecule. MATERIALS AND METHODSBacterial Strains, Plasmids, and Bacteriophages. The E. coli s...

show abstract

Mechanism of phage Mu-1 integration: nalidixic acid treatment causes clustering of Mu-1-induced mutations near replication origin.

Abstract: to 1, starting from the point of origin of DNA replication to the termini of DNA replication. These results are compatible with the idea that Mu-i integrates at the replication fork.

Cited by 14 publications

References 26 publications

Microarray analysis of Mu transposition in Salmonella enterica, serovar Typhimurium: transposon exclusion by high‐density DNA binding proteins

Microarray analysis of Mu transposition in Salmonella enterica, serovar Typhimurium: transposon exclusion by high‐density DNA binding proteins

Replication forks of Escherichia coli are not the preferred sites for lysogenic integration of bacteriophage Mu

Recombination involving transposable elements: role of target molecule replication in Tn1 delta Ap-mediated replicon fusion.

Contact Info

Product

Resources

About