Viral terminal protein directs early organization of phage DNA replication at the bacterial nucleoid

摘要

The mechanism leading to protein-primed DNA replication has been studied extensively in vitro. However, little is known about the in vivo organization of the proteins involved in this fundamental process. Here we show that the terminal proteins (TPs) of phages 4)29 and PRD1, infecting the distantly related bacteria Bacillus 'subtilis and Escherichia coli, respectively, associate with the host bacterial nucleoid independently of other viral-encoded proteins. Analyses of phage φ29 revealed that the TP N-terminal domain (residues 1-73) possesses sequence-independent DNA-binding capacity and is responsible for its nucleoid association. Importantly, we show that in the absence of the TP N-terminal domain the efficiency of 4>29 DNA replication is severely affected. Moreover, the TP recruits the phage DNA polymerase to the bacterial nudeoid, and both proteins later are redistributed to enlarged helix-like structures in an MreB cytoskeleton-dependent way. These data disclose a key function for the TP in vivo: organizing the early viral DNA replication machinery at the cell nucleoid.