TY - JOUR
T1 - The role of template superhelicity in the initiation of bacteriophage λ DNA replication
AU - Alfano, Christine
AU - Mcmacken, Roger
N1 - Funding Information:
We thank Mark Dodson, Harrison Echols, Ross Inman and Arthur Kornberg for communication of unpublished infarnation. We also thank Todd Seeley of this department for his help In the preparation of Figure 5. This work was supported by grants OC2253 and CTG6526 from the NTH.
PY - 1988/10/25
Y1 - 1988/10/25
N2 - The preptriming steps in the initiation of bactericphage λ DNA replication depend on the action of the λ O and P proteins and on the DnaB helicase, single-stranded DNA binding protein (SSB), and DnaJ and DnaK heat shock proteins of the E. coli host. The binding of multiple copies of the λ O protein to the phage replication origin (oriλ) initiates the ordered assembly of a series of nucleoprotein structures that form at oriλ prior to DNA unwinding, priming and DNA synthesis steps. Since the initiation of A DNA replication is known to occur only on supercoiled templates in vivoand in vitro, We examined how the early steps in A DNA replication are influenced by superhelical tension. All initiation complexes formed prior to helicase-mediated DNA-unwinding form with high efficiency on relaxed oriλ DNA. Nonetheless, the DNA templates in these structures must be negatively super-twisted before they can be replicated. Once DNA helicase unwinding is initiated at oriλ, however, later steps in A DNA replication proceed efficiently in the absence of superhelical tension. We conclude that supercoiling is required during the initiation of A DNA replication to facilitate entry of a DNA helicase, presumably the DnaB protein, between the DNA strands.
AB - The preptriming steps in the initiation of bactericphage λ DNA replication depend on the action of the λ O and P proteins and on the DnaB helicase, single-stranded DNA binding protein (SSB), and DnaJ and DnaK heat shock proteins of the E. coli host. The binding of multiple copies of the λ O protein to the phage replication origin (oriλ) initiates the ordered assembly of a series of nucleoprotein structures that form at oriλ prior to DNA unwinding, priming and DNA synthesis steps. Since the initiation of A DNA replication is known to occur only on supercoiled templates in vivoand in vitro, We examined how the early steps in A DNA replication are influenced by superhelical tension. All initiation complexes formed prior to helicase-mediated DNA-unwinding form with high efficiency on relaxed oriλ DNA. Nonetheless, the DNA templates in these structures must be negatively super-twisted before they can be replicated. Once DNA helicase unwinding is initiated at oriλ, however, later steps in A DNA replication proceed efficiently in the absence of superhelical tension. We conclude that supercoiling is required during the initiation of A DNA replication to facilitate entry of a DNA helicase, presumably the DnaB protein, between the DNA strands.
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U2 - 10.1093/nar/16.20.9611
DO - 10.1093/nar/16.20.9611
M3 - Article
C2 - 2847118
AN - SCOPUS:0024297218
SN - 0305-1048
VL - 16
SP - 9611
EP - 9630
JO - Nucleic acids research
JF - Nucleic acids research
IS - 20
ER -