Bypass of a nick by the replisome of bacteriophage T7.

Abstract:

DNA polymerase and DNA helicase are essential components of DNA replication. The helicase unwinds duplex DNA to provide single-stranded templates for DNA synthesis by the DNA polymerase. In bacteriophage T7, movement of either the DNA helicase or the DNA polymerase alone terminates upon encountering a nick in duplex DNA. Using a minicircular DNA, we show that the helicase/polymerase complex can bypass a nick, albeit at reduced efficiency of 7%, on the non-template strand to continue rolling-circle DNA synthesis. A gap in the non-template strand cannot be bypassed. The efficiency of bypass synthesis depends on the DNA sequence downstream of the nick. A nick on the template strand cannot be bypassed. Addition of T7 single-stranded DNA binding protein to the complex stimulates nick-bypass two-fold. We propose that the association of helicase with the polymerase prevents dissociation of the helicase upon encountering a nick, allowing the helicase to continue unwinding of the duplex downstream of the nick.

Polymerases:

T7

Topics:

Accessory Proteins/Complexes, Nick Extension

Status:

new topics/pols set partial results complete validated

Results:

Polymerase Reference Property Result Context
T7 Zhu B2011 Nucleotide incorporation accessory protein(s) Helicase
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