Single-Stranded DNA Transposition Is Coupled to Host Replication

SummaryDNA transposition has contributed significantly to evolution of eukaryotes and prokaryotes. Insertion sequences (ISs) are the simplest prokaryotic transposons and are divided into families on the basis of their organization and transposition mechanism. Here, we describe a link between transposition of IS608 and ISDra2, both members of the IS200/IS605 family, which uses obligatory single-stranded DNA intermediates, and the host replication fork. Replication direction through the IS plays a crucial role in excision: activity is maximal when the “top” IS strand is located on the lagging-strand template. Excision is stimulated upon transient inactivation of replicative helicase function or inhibition of Okazaki fragment synthesis. IS608 insertions also exhibit an orientation preference for the lagging-strand template and insertion can be specifically directed to stalled replication forks. An in silico genomic approach provides evidence that dissemination of other IS200/IS605 family members is also linked to host replication.

Graphical AbstractFigure optionsDownload high-quality image (202 K)Download as PowerPoint slideHighlights
► IS200/IS605 family single-stranded DNA transposition is coupled to replication forks
► Replication direction through the IS plays a crucial role in activating IS excision
► Helicase or primase inhibition stimulates IS excision from the lagging strand
► Insertion shows a lagging-strand preference in normal and blocked forks