The Isometric Single-Stranded DNA Phages

Denhardt, David T.

doi:10.1007/978-1-4684-2712-7_1

Cited by 25 publications

(8 citation statements)

References 288 publications

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“…That it is made by all the isometric phages examined and that it seemingly has a counterpart in the filamentous phages (8) implies that it is advantageous if not necessary for some aspect of the viral life cycle. Its actions on ssDNA suggest a role in superinfection exclusion (7). Other possible roles include shutting off host cell DNA synthesis and facilitating the transition from RF replication to DNA synthesis (10,11,13,17,23).…”

Section: Discussionmentioning

confidence: 99%

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Expression of the cloned bacteriophage phi X174 A* gene in Escherichia coli inhibits DNA replication and cell division

Colasanti¹,

Denhardt²

1985

J Virol

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The A* gene of bacteriophage 4X174 has been cloned into the inducible expression vector pCQV2 under conditions allowing its lethal action to be controlled by the XcI857 repressor. Upon induction of expression, DNA synthesis in Escherichia coli carrying the recombinant plasmid is severely inhibited; however, these same cells permit 1-galactosidase induction at a rate similar to that observed in control cells at the inducing (for A*) temperature. Cells in which A* is expressed form ifiaments and produce more RecA protein, indicating at least a partial induction of the SOS response; however, there is no evidence of damage to the bacterial chromosome. It appears that the A* protein has as one function the inhibition of cell division and DNA replication but not transcription or protein synthesis during phage infection.

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Section: Discussionmentioning

confidence: 99%

“…This protein was later found to be a product of the A (or A*) gene (13,23). These studies, however, did not reach a clear and unambiguous position regarding the role of A* protein (7). A more recent study has shown that A* has the ability to inhibit replication of both replicative form (RF) and DNA singlestranded (ssDNA) XX174 in vitro (11).…”

mentioning

confidence: 99%

Expression of the cloned bacteriophage phi X174 A* gene in Escherichia coli inhibits DNA replication and cell division

Colasanti¹,

Denhardt²

1985

J Virol

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“…(ssDNA) to the covalently closed duplex, parental replicative form (RF) (1,2). This ssDNA --RF conversion has been successfully reconstituted in vitro and requires 11 Escherichia coli proteins (3).…”

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confidence: 99%

“…With completion of the ssDNA -* RF conversion, the parental RF is duplicated to produce multiple RF copies (RF -* RF) prior to selective synthesis of viral ssDNA for packaging into progeny phage (1,2). In the RF duplication reaction, the viral and complementary strands are replicated by distinct mechanisms.…”

mentioning

confidence: 99%

Conservation of the primosome in successive stages of phi X174 DNA replication.

Low¹,

Arai²,

Kornberg³

1981

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

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Synthesis of a complementary strand to match the single-stranded, circular, viral (+) DNA strand of phage phi X174 creates a parental duplex circle (replicative form, RF). This synthesis is initiated by the assembly and action of a priming system, called the primosome [Arai, K. & Kornberg, A (1981) Proc. Natl. Acad. Sci. USA 78, 69-73; Arai, K., Low, R. L. & Kornberg, A. (1981) Proc. Natl. Acad. Sci. USA 78, 707-711]. Of the seven proteins that participate in the assembly and function of the primosome, most all of the components remain even after the DNA duplex is completed and covalently sealed. Remarkably, the primosome in the isolated RF obviates the need for supercoiling of RF by DNA gyrase, an action previously considered essential for the site-specific cleavage by gene A protein that starts viral strand synthesis in the second stage of phi X174 DNA replication. Finally, priming of the synthesis of complementary strands on the nascent viral strands to produce many copies of progeny RF utilizes the same primosome, requiring the addition only of prepriming protein i. thus a single primosome, which becomes associated with the incoming viral DNA in the initial stage of replication, may function repeatedly in the initiation of complementary strands at the subsequent stage of RF multiplication. These patterns of phi X174 DNA replication suggest that a conserved primosome also functions in the progress of the replicating fork of the Escherichia coli chromosome, particularly in initiating the synthesis of nascent (Okazaki) fragments.

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“…Replication of bacteriophage 4X174 (OX) DNA in Escherichia coli proceeds by three stages: SS --RF, conversion of the single-stranded viral (+) circle (SS) to duplex replicative form (RF); RF --RF, multiplication of RF; and RF --SS, selective synthesis of viral strands for virions, using the complementary (-) strand of RF as template (1,2).…”

mentioning

confidence: 99%

Replication of duplex DNA of phage phi X174 reconstituted with purified enzymes.

Arai¹,

Arai²,

Shlomai³

et al. 1980

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

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Replication of the covalently closed duplex replicative form (RF) of phage gX174 DNA has been achieved by couplin two known enzyme systems: (i) synthesis of viral strand circles (SS) from RF, and (if) conversion of SS to nearly complete RF (RF II. In this coupled system, activated RF (gene A-RF II complex) was a more efficient template and generated as many as 10 RF II molecules per RF input, at a rate commensurate with SS synthesis. The (12,13). One system (RF --SS) requires the participation of OX-encoded gene A protein, host rep protein, SSB, and DNA polymerase III holoenzyme to produce multiple copies of covalently closed, single-stranded viral circles from RF I. Replication is initiated by gene A protein, which creates a nick in the viral strand at the origin of RF replication (14-16). Synthesis by holoenzyme of viral strands, facilitated by helicase action of rep protein (17), proceeds by a looped rolling-circle mechanism (13).The second system needed for RF synthesis is the initial reaction of complementary strand synthesis (SS --RF); the nascent viral strands now provide the template for complementary strand synthesis. Thus, viral and complementary strands are synthesized by distinct mechanisms (5, 14), analogous to the continuous and discontinuous mechanisms proposed in host chromosome synthesis (7,14). Although synthetic viral strands isolated from the RF --SS reaction were shown to serve as templates for the conversion of SS to RF (18), the reagents for the latter reaction strongly inhibited the RF --SS reaction. With more extensive purification of the numerous proteins required for both of these stages, coupling of the SS -RF with the RF SS reactions has been achieved and is the subject of this report. Operation of the coupled system now provides an opportunity to investigate basic questions about the mechanisms of viral and complementary strand synthesis in RF duplication. MATERIALS AND METHODS MaterialsBuffer A is 0.1 M Tris-HCI (pH 7.5), 20% (wt/vol) sucrose, 40 mM dithiothreitol, and bovine serum albumin at 0.2 mg/ml; buffer B is 0.1 M Tris-HCl (pH 8.1), 50 mM MgCl2, 5 mM dithiothreitol, bovine serum albumin at 0.5 mg/ml, and 50% (vol/vol) glycerol; buffer C is 0.02 M Tris-HCI (pH 8.1), 1 M NaCl, 5 mM EDTA, bovine serum albumin at 0.1 mg/ml, 1 mM dithiothreitol, and 10% (vol/vol) glycerol.Extensively purified E. coli replication proteins were: rep protein (4 X 107 units/mg) (19), gene A protein* (5.5 X 106 units/mg) (20), and dUTPase (2 X 107 units/mg) (18). The other replication proteins were as described (21). RNA polymerase holoenzyme (22)

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The Isometric Single-Stranded DNA Phages

Cited by 25 publications

References 288 publications

Expression of the cloned bacteriophage phi X174 A* gene in Escherichia coli inhibits DNA replication and cell division

Expression of the cloned bacteriophage phi X174 A* gene in Escherichia coli inhibits DNA replication and cell division

Conservation of the primosome in successive stages of phi X174 DNA replication.

Replication of duplex DNA of phage phi X174 reconstituted with purified enzymes.

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