Host factors that promote transpososome disassembly and the PriA-PriC pathway for restart primosome assembly.
Initiation of bacteriophage Mu DNA replication by transposition requires the disassembly of the transpososome that catalyses strand exchange and the assembly of a replisome promoted by PriA, PriB, PriC and DnaT proteins, which function in the host to restart stalled replication forks. Once the molecular chaperone ClpX weakens the very tight binding of the transpososome to the Mu ends, host disassembly factors (MRFalpha-DF) promote the dissociation of the transpososome from the DNA template and the assembly of a new nucleoprotein complex. Prereplisome factors (MRFalpha-PR) further alter the complex, allowing PriA binding and loading of major replicative helicase DnaB onto the template promoted by the restart proteins. MRFalpha-PR is essential for DnaB loading by restart proteins even on the deproteinized Mu fork whereas MRFalpha-DF is not required on the deproteinized template. When the transition from transpososome to replisome was reconstituted using MRFalpha-DF and MRFalpha-PR, initiation of Mu DNA replication was strictly dependent upon added PriC and PriA helicase. In contrast, initiation on the deproteinized template was predominantly dependent upon PriB and did not require PriA's helicase activity. The results indicate that transition mechanisms beginning with the transpososome disassembly can determine the pathway of replisome assembly by restart proteins.
North
Stella H
SH
Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Room 331 Basic Science Bldg., 3900 Reservoir Road NW, Washington, DC 20057-1455, USA.
Nakai
Hiroshi
H
D000251:Adenosine Triphosphatases / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D010583:Bacteriophage mu / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure*; D004265:DNA Helicases / Q000378:metabolism; D004261:DNA Replication; D004279:DNA, Viral / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000378:metabolism; D053488:DnaB Helicases; D004926:Escherichia coli / Q000235:genetics / Q000648:ultrastructure* / Q000821:virology; D029968:Escherichia coli Proteins / Q000378:metabolism*; D019895:Transposases / Q000378:metabolism*
D001426:Bacterial Proteins; D004279:DNA, Viral; D004268:DNA-Binding Proteins; C104198:DnaT protein, E coli; D029968:Escherichia coli Proteins; C069996:PriB protein (N-terminal); C069995:PriC protein, E coli; C114697:mu transposase; D019895:Transposases; D000251:Adenosine Triphosphatases; C506730:dnaB protein, E coli; C506743:priA protein, E coli; D004265:DNA Helicases; D053488:DnaB Helicases