Protein-primed DNA replication: a transition between two modes of priming by a unique DNA polymerase

EMBO J. 1997 May 1;16(9):2519-27. doi: 10.1093/emboj/16.9.2519.


Phage phi29 from Bacillus subtilis is a paradigm of the protein-primed replication mechanism, in which a single-subunit DNA polymerase is involved in both the specific protein-primed initiation step and normal DNA elongation. To start phi29 DNA replication, the viral DNA polymerase must interact with a free molecule of the viral terminal protein (TP), to prime DNA synthesis once at each phi29 DNA end. The results shown in this paper demonstrate that the DNA polymerase-primer TP heterodimer is not dissociated immediately after initiation. On the contrary, there is a transition stage in which the DNA polymerase synthesizes a five nucleotide-long DNA molecule while complexed with the primer TP, undergoes some structural change during replication of nucleotides 6-9, and finally dissociates from the primer protein when nucleotide 10 is inserted onto the nascent DNA chain. This behaviour probably reflects the polymerase requirement for a DNA primer of a minimum length to efficiently catalyze DNA elongation. The significance of such a limiting transition stage is supported by the finding of abortive replication products consisting of the primer TP linked up to eight nucleotides, detected during in vitro replication of phi29 TP-DNA particularly under conditions that decrease the strand-displacement capacity of phi29 DNA polymerase.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacillus Phages / genetics*
  • Catalysis
  • DNA Mutational Analysis
  • DNA Primers / metabolism
  • DNA Replication*
  • DNA, Viral / biosynthesis*
  • DNA, Viral / chemistry
  • DNA-Directed DNA Polymerase / metabolism*
  • Dimerization
  • Models, Genetic
  • Templates, Genetic
  • Viral Proteins / metabolism*


  • DNA Primers
  • DNA, Viral
  • Viral Proteins
  • terminal protein, Bacillus phage phi29
  • DNA-Directed DNA Polymerase