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Science 13 December 1974:
Vol. 186. no. 4168, pp. 987 - 993
DOI: 10.1126/science.186.4168.987
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Articles

Multienzyme Systems of DNA Replication

Randy Schekman 1, Alan Weiner 1, and Arthur Kornberg 1

1 Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305

Replication is accomplished by multienzyme systems whose operations are usefully considered in respect to three stages of the process: initiation, elongation, anid termination.

1) Initiation entails synthesis of a short RNA fragment that serves as primer for the elongation step of DNA synthesis. This stage, probed by SS phage DNA templates, reveals three distinctive and highly specific systems in E. coli. The Ml3 DNA utilizes RNA polymerase in a manner that may reflect how plasmid elements are replicated in the cell. The ØX174 DNA does not rely on RNA-polymerase, but requires instead five distinctive proteins which may belong to an apparatus for initiating a host chromosome replication cycle at the origin. The G4 DNA, also independent of RNA polymerase, needs simply the dnaG protein for its distinctive initiation and may thus resemble the system that initiates the replication fragments at the nascent growing fork. In each case it is essential that in vitro the DNA-unwinding protein coat the viral DNA and influence its structure.

2) Elongation is achieved in every case by the multisubunit, holoenzyme form of DNA polymerase III. Copolymerase III, which is an enzyme subunit, and adenosine triphosphate are required to form a proper complex with the primer template but appear dispensable for the ensuing chain growth by DNA polymerase (33).

3) Termination requires excision of the RNA priming fragment, filling of gaps and sealing of interruptions to produce a covalently intact phosphodiester backbone. DNA polymerase I has the capacity for excision and gapfilling and DNA ligase is required for sealing.

What once appeared to be a simple DNA polymerase-mediated conversion of a single-strand to a duplex circle (34) is now seen as a complex series of events in which diverse multienzyme systems function. Annoyance with the difficulties in resolving and reconstituting these systems is tempered by the conviction that these are the very systems used ,by the cell in replicating its chromosome and extrachromosomal elements. Thus, understanding of the regulation of replication events in the cell, their localization at membrane surfaces and integration with cell division, and their coordination with phage DNA maturation and particle assembly will all be advanced by knowledge of the components of the replicative machinery.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Crystal Structure of PriB, a Primosomal DNA Replication Protein of Escherichia coli.
J.-H. Liu, T.-W. Chang, C.-Y. Huang, S.-U. Chen, H.-N. Wu, M.-C. Chang, and C.-D. Hsiao (2004)
J. Biol. Chem. 279, 50465-50471
   Abstract »    Full Text »    PDF »
Excision-Repair of Uracil in DNA: Its Implications for the Discontinuous Replication of DNA In Vivo and In Vitro.
I. R. Lehman, B.-K. Tye, and P.-O. Nyman (1979)
Cold Spring Harb Symp Quant Biol 43, 221-230
   Abstract »    PDF »
DNA Replication Proteins of Escherichia coli and Phage {lambda}.
S. H. Wickner (1979)
Cold Spring Harb Symp Quant Biol 43, 303-310
   Abstract »    PDF »
Single-stranded Phage Replication: Positive- and Negative-strand DNA Synthesis.
J. Sims, K. Koths, and D. Dressler (1979)
Cold Spring Harb Symp Quant Biol 43, 349-365
   Abstract »    PDF »
The Intergenic Region and the Origins for Filamentous Phage DNA Replication.
H. Schaller (1979)
Cold Spring Harb Symp Quant Biol 43, 401-408
   Abstract »    PDF »
DNA Replication by Bacteriophage T4 Proteins: Role of the DNA-delay Gene 61 in the Chain-initiation Reaction.
L. L. Silver and N. G. Nossal (1979)
Cold Spring Harb Symp Quant Biol 43, 489-494
   Abstract »    PDF »


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Science. ISSN 0036-8075 (print), 1095-9203 (online)