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bioRxiv · 10.1101/2020.12.21.423798

Disintegration promotes proto-spacer integration by the Cas1-Cas2 complex

Ma, C.-H.·Javanmardi, K.·Finkelstein, I. J.·Jayaram, M.
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Abstract

Disintegration--the reversal of transposon DNA integration at a target site--is regarded as an abortive off-pathway reaction. Here we challenge this view with a biochemical investigation of the mechanism of protospacer insertion by the Streptococcus pyogenes Cas1-Cas2 complex, which is mechanistically analogous to DNA transposition. In supercoiled target sites, the predominant outcome is the disintegration of one-ended insertions that fail to complete the second integration event. In linear target sites, one-ended insertions far outnumber complete proto-spacer insertions. The second insertion event is most often accompanied by disintegration of the first, mediated either by the 3-hydroxyl exposed during integration or by water. One-ended integration intermediates may mature into complete spacer insertions via DNA repair pathways that are also involved in transposon mobility. We propose that disintegration-promoted integration is functionally important in the adaptive phase of CRISPR-mediated bacterial immunity, and perhaps in other analogous transposition reactions.

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Ma, C.-H., Javanmardi, K., Finkelstein, I. J., Jayaram, M.. 2020-12-21. Disintegration promotes proto-spacer integration by the Cas1-Cas2 complex. https://doi.org/10.1101/2020.12.21.423798

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