Document Type



Medicine and Health Sciences


The replication of herpes simplex virus type 1 (HSV-1) is associated with a high degree of homologous recombination, which is likely to be mediated, in part, by HSV-1-encoded proteins. We have previously shown that the HSV-1 encoded ICP8 protein and alkaline nuclease UL12 are capable of catalyzing an in vitro strand-exchange reaction. Here, we show, by electron microscopy, that the products of the strand exchange reaction between linear double-stranded DNA and circular single-stranded DNA consist of the expected joint molecule forms: sigma, alpha, and gapped circles. Other exonucleases, such as lambda Red α, which, like UL12, digests 5′-3′, as well as Escherichia coli exonuclease III (ExoIII), which digests 3′-5′, could substitute for UL12 in the strand exchange reaction by providing a resected DNA end. ICP8 generated the same intermediates and strand exchange products when the double-stranded DNA substrate was preresected by any of the nucleases. Using substrates with large regions of non-homology we found that pairing by ICP8 could be initiated from the middle of a DNA molecule and did not require a homologous end. In this reaction, the resection of a DNA end by the nuclease is required to reveal homologous sequences capable of being paired by ICP8. This study further illustrates the complexity of the multi-functional ICP8 protein.


J Mol Biol. Author manuscript; available in PMC 2015 Apr 28. Published in final edited form as: J Mol Biol. 2004 Sep 3; 342(1): 57–71. doi: 10.1016/j.jmb.2004.07.012 PMCID: PMC4412345 NIHMSID: NIHMS209311