Participation of Escherichia coli DNA in the replication of temperate bacteriophage Mu1

Schroeder, W.; Bade, Ernesto G.; Delius, Hajo

doi:10.1016/0042-6822(74)90347-x

Cited by 45 publications

(17 citation statements)

References 18 publications

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“…It is known that heterogeneous covalently closed circles containing Mu and host sequences are formed during the productive cycle of Mu (14,15). It has been pointed out that nonhomologous sequences in mature virions could be derived from these circles (15). However, the mechanism by which these circles are generated and the exact function of these circles in the Mu development are not clear.…”

Section: Discussionmentioning

confidence: 99%

“…7, are that (1) mu DNA is packaged into virion heads from maturation precursors which have covalently linked Mu DNA and host DNA; (2) the packaging starts specifically at the c end of Mu DNA in a maturation precursor and proceeds unidirectionally toward the other end of Mu; and (3) the Mu genome alone cannot fill the heads adequately and therefore some host DNA, covalently linked to Mu DNA, is packaged during morphogenesis. It is known that heterogeneous covalently closed circles containing Mu and host sequences are formed during the productive cycle of Mu (14,15). It has been pointed out that nonhomologous sequences in mature virions could be derived from these circles (15).…”

Section: Discussionmentioning

confidence: 99%

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Influence of insertions on packaging of host sequences covalently linked to bacteriophage Mu DNA.

Bukhari¹,

Taylor²

1975

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

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Insertions in bacteriophage Mu DNA have been identified. These insertions are responsible for at least seven X mutations, all of which eliminate essential Mu functions. The insertions are about 800 base pairs long and are located to the left of the cleavage site of restriction endonuclease EcoRI, near the immunity end of Mu DNA. We have found that such-insertions cause a reduction in the length of nonhomologous terminal sequences which are seen as split ends in denatured and renatured Mu DNA molecules. These heterogeneous sequences apparently arise from packaging of host DNA from maturation precursors in which Mu and host DNA are covalently linked. We infer that a single Mu genome length is too short to be cut during morphogenesis, and thus some host DNA is packaged into mature virions. Since the insertions increase the length of Mu DNA, they decrease the amount of host DNA needed for packaging.The temperate bacteriophage Mu is characterized by the highly promiscuous integration of its DNA into the genome of its host bacterium Escherichia coli (1-3). The prophage Mu DNA can be excised precisely from the different integration sites, and as a result wild-type function of the gene into which Mu was inserted can be restored (4). This reversal of Mu integration can be seen if the prophages contain the X mutations, which block the lethal and essential phage functions.Mu X mutants revert to wild type at a frequency of about 10-8. However, no X amber mutants have been found. Thus, we proposed that the X mutations are insertions (4). We have investigated the nature of the X mutations by agarose-gel electrophoresis of Mu DNA fragments produced by specific endonucleases, and by electron microscopic examination of Mu DNA heteroduplexes. These studies have shown that the X mutations are insertions near the immunity (c) end of Mu DNA. In one X mutant, the insertion is demonstrated to be of about 720 base pairs, located 4 kilobases (kb) away from the c end.The isolation of insertions in Mu DNA has allowed us to analyze further some aspects of Mu DNA structure. Mu DNA, a double-stranded linear duplex of about 37 kb (5), has some interesting features. When it is denatured and reannealed, two types of homoduplex molecules are obtained (Fig. 1). All the molecules show single-stranded tails or split ends, measuring about 4% of the molecular length. The split ends, which apparently represent sequences picked up randomly from the, E. coli chromosome, are always found at the S gene end, called here the SE end, of Mu DNA (6-8). Some molecules show another nonrenaturable region, termed the G bubble, near the SE end (9). Recently, we observed that the c end of Mu DNA is also not fixed, and probably varies in length by about 100 base pairs (10, 11).Abbreviation: kb, kilobase. t To whom correspondence should be directed.One plausible model for the origin of the heterogeneity of the SE end is that Mu DNA is packaged into phage heads from maturation precursors which contain both Mu DNA and host sequences. This hypothesis implies that...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Influence of insertions on packaging of host sequences covalently linked to bacteriophage Mu DNA.

Bukhari¹,

Taylor²

1975

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

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“…The model put forward by A. Campbell, which neatly fits the relevant behavior of X and P2, would need more than a trivial adaptation for explaining Mu-i integration. The fact that during the lytic cycle Mu-i DNA is found covalently linked to bacterial DNA (19,20) leads us to the assumption that it is obligatory for this phage to bind to the host chromosome.…”

Section: Discussionmentioning

confidence: 99%

“…Immediately after infection, Mu-i DNA is covalently linked to the host DNA (19,20). The nucleotide sequence of this bacterial DNA portion varies from particle to particle (18)(19)(20)(21). These observations lead to the conclusion that Mu-i has some sort of function that allows its association with the host genome at a high frequency and, furthermore, could be essential to its replication process.…”

mentioning

confidence: 99%

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

Paolozzi¹,

Jucker²,

Calef³

1978

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

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“…The reactions were stopped by adding SDS to a final concentration of I % (w/v) and heating to 60 "C for 2 min. A 0-1 ml sample was then layered on to a 5 to 20 % (w/v) neutral sucrose gradient (Schroder et al, 1974), together with 32P-labelled marker DNA, and centrifuged in a Beckman S W 50. I rotor at 40000 rev.…”

Section: E T H O D Smentioning

confidence: 99%

A Salmonella typhimurium Endonuclease that Converts Native DNA to Fragments of about 8 X 105 daltons

Schumann

Bade

1977

Journal of General Microbiology

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319Crude extracts of Salmonella typhimurium were found to contain an endonuclease that degraded double-stranded linear DNA from bacteria and phages to fragments with a molecular weight of about 8 x 105. The nuclease did not have an absolute requirement for Mg2+. One discrete intermediate product had a molecular weight of 6.6 x I O~. Extracts from two different mutants were tested : one completely lacked the endonuclease activity (strain DB5575), and the other showed an absolute requirement for Mg2+ (strain 4543). No biological role has yet been found for this endonuclease of S. typhimurium.

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Participation of Escherichia coli DNA in the replication of temperate bacteriophage Mu1

Cited by 45 publications

References 18 publications

Influence of insertions on packaging of host sequences covalently linked to bacteriophage Mu DNA.

Influence of insertions on packaging of host sequences covalently linked to bacteriophage Mu DNA.

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

A Salmonella typhimurium Endonuclease that Converts Native DNA to Fragments of about 8 X 105 daltons

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