@article{Stachler_Wortz_Alkhnbashi-Adapt_induc_self-JBC2020,
author = {Stachler, Aris-Edda and Wortz, Julia and Alkhnbashi, Omer 
          S. and Turgeman-Grott, Israela and Smith, Rachel and Allers, 
          Thorsten and Backofen, Rolf and Gophna, Uri and Marchfelder, 
          Anita},
title = {Adaptation induced by self-targeting in a type {I}-{B} 
         {CRISPR}-{Cas} system},
journal = {JBC},
year = {2020},
doi = {10.1074/jbc.RA120.014030},
volume = {295},
user = {alkhanbo},
pmid = {32723866},
pages = {13502-13515},
number = {39},
issn = {1083-351X},
abstract = {Haloferax volcanii is, to our knowledge, the only 
            prokaryote known to tolerate CRISPR-Cas-mediated damage to 
            its genome in the WT background; the resulting cleavage of 
            the genome is repaired by homologous recombination restoring 
            the WT version. In mutant Haloferax strains with enhanced 
            self-targeting, cell fitness decreases and 
            microhomology-mediated end joining becomes active, 
            generating deletions in the targeted gene. Here we use 
            self-targeting to investigate adaptation in H. volcanii 
            CRISPR-Cas type I-B. We show that self-targeting and genome 
            breakage events that are induced by self-targeting, such as 
            those catalyzed by active transposases, can generate DNA 
            fragments that are used by the CRISPR-Cas adaptation 
            machinery for integration into the CRISPR loci. Low cellular 
            concentrations of self-targeting crRNAs resulted in 
            acquisition of large numbers of spacers originating from the 
            entire genomic DNA. In contrast, high concentrations of 
            self-targeting crRNAs resulted in lower acquisition that was 
            mostly centered on the targeting site. Furthermore, we 
            observed naive spacer acquisition at a low level in WT 
            Haloferax cells and with higher efficiency upon 
            overexpression of the Cas proteins Cas1, Cas2, and Cas4. 
            Taken together, these findings indicate that naive 
            adaptation is a regulated process in H. volcanii that 
            operates at low basal levels and is induced by DNA breaks.}
}