CRISPR virus-plasmid defence-regulatory system
Almost all archaeal chromosomes and some conjugative plasmids contain one or more clusters of short regularly inter-spaced repeats (CRISPR) some of which constitute over 100 repeat-spacer units. These have been implicated in inhibiting propagation of viruses and plasmids in archaea (and in many bacteria) via an intermediate RNA mechanism (Tang et al., 2002; Tang et al., 2005; Mojica et al., 2005). Our laboratory has identified the protein which specifically binds to crenarchaeal repeats (Peng et al., 2003) and the processing products of the cluster-encoded transcripts from each DNA strand (Lillestøl et al., 2006). We are currently exploiting bioinformatic approaches (Vestergaard et al., 2008; Shah et al., 2008) and genetic experiments, to understand the dynamic interactions between chromosomal clusters and extra-chromosomal elements.