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Bacterial Replication Fork: Synthesis of Lagging Strand

  1. Taku Tanaka,
  2. Hisao Masai

Published Online: 19 APR 2010

DOI: 10.1002/9780470015902.a0001049.pub2



How to Cite

Tanaka, T. and Masai, H. 2010. Bacterial Replication Fork: Synthesis of Lagging Strand. eLS. .

Author Information

  1. Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan

Publication History

  1. Published Online: 19 APR 2010


How can an antiparallel DNA (deoxyribonucleic acid) strand be duplicated by a DNA polymerase that synthesises DNA in only one direction? This paradox of DNA synthesis on the lagging strand was dissolved by discovery of Okazaki fragments. The major components of the bacterial replication fork include replicative helicase, primase and DNA polymerase. The loading of replicative helicase, DnaB, is the most critical step for assembly of a primosome, a protein complex responsible for duplex unwinding and primer RNA (ribonucleic acid) synthesis at the replication fork. DNA polymerase may be an asymmetric dimer, each of which may concurrently synthesise leading or lagging strand. Several different modes of primosome assembly have been identified in bacteria. At oriC (origin of chromosome), DnaA-dependent primosome is assembled for initiation of a round of DNA replication, whereas PriA-dependent primosome is assembled at stalled replication forks to facilitate replication restart.

Key Concepts:

  • Initiation of DNA replication: DNA replication is initiated by the initiator protein, which specifically recognises and binds to the origin sequence and recruits other primosome components including a DNA helicase.

  • Leading and lagging strands: Leading strand is the one in which the direction of DNA chain elongation and overall fork movement is the same and lagging strand is the one in which they are opposite.

  • Replicative helicase: An enzyme which catalyses continuous unwinding of the parental duplex DNA at the replication fork.

  • Replication fork: The site of DNA replication where two replicating single-stranded DNA separates.

  • Primer RNA: A short stretch of RNA, the 3′-terminus of which is utilised by DNA polymerases for DNA elongation.

  • Primosome: A name given to the protein complex capable of duplex DNA unwinding and primer RNA synthesis at the replication fork.

  • Stalled replication fork: A replication fork the movement of which is blocked by internal and external ‘replication stress’ including DNA damages and depletion of nucleotide precursors.

  • Replication restart: The process of reassembly of primosome at a stalled replication fork to resume DNA chain elongation.


  • replication fork;
  • Okazaki fragment;
  • DNA polymerases;
  • primer RNA;
  • replication restart