More recently, TE related to CRISPRs, Casposons have been identified (Krupovic et al., 2014) and a reassement of their ends has led to the
identification of an 14-15 bp target duplication (Hickman & Dyda, 2014). Moreover, the
purified Cas1 enzyme encoded by these ancestral transposons has been
demonstrated to catalyse strand transfer of a pre-cleaved transposon in vitro but does not appear to promote
transposon strand cleavage in this assay (Hickman
& Dyda, 2015). Cas1 "casposases" use
similar chemistry to that used by the CRISPR Cas1-Cas2 complex but with opposite
substrate specificities since CRISPR Cas1-Cas2 integrates "random" sequences
into a specific site in the CRISPR locus whereas casposases integrate specific site (the casposon ends) into
random target sequences.
AB & Dyda F (2014) CRISPR-Cas immunity and mobile DNA: a new superfamily of
DNA transposons encoding a Cas1 endonuclease. Mob DNA 5: 23.
AB & Dyda F (2015) The casposon-encoded Cas1 protein from Aciduliprofundum
boonei is a DNA integrase that generates target site duplications. Nucleic Acids Res 43: 10576-10587.
- Krupovic M, Makarova KS, Forterre P,
Prangishvili D & Koonin EV (2014) Casposons: a new superfamily of
self-synthesizing DNA transposons at the origin of prokaryotic CRISPR-Cas
immunity. BMC Biol 12: 36.