Figure 2.

Schematic mechanism of intasome assembly. Under the right biochemical conditions, an oligomer of IN proteins assembles on the ends of vDNA to form the stable synaptic complex (SSC). IN then cleaves two nucleotides from the 3′ ends of vDNA, forming the cleaved synaptic complex (CSC) that exposes the conserved free 3′-OH groups of the catalytically competent CA dinucleotides. CSC intasomes can capture tDNA to form the target capture complex (TCC), which will rapidly catalyze strand transfer to form the post-catalytic strand transfer complex (STC) in which the tDNA and the integrated vDNA are still bound to the intasome. In this schematic, there are two oligonucleotides that mimic the two long-terminal repeats of vDNA ends, which facilitates in vitro assembly and biochemical/structural studies. However, in a cell, these would be replaced by a single vDNA genome containing long-terminal repeats on each end, respectively.