The Repetitive DNA Elements Called CRISPRs and Their Associated Genes: Evidence of Horizontal Transfer Among Prokaryotes
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We have found direct DNA repeats 21–47 bp in length interspersed with nonrepetitive sequences of similar length, or clustered regularly interspaced short palindromic repeats (CRISPRs) in a wide range of diverse prokaryotes, including many Archaeal and Eubacterial species. A number of cas, CRISPR-associated genes have also been characterized in many of the same organisms. Phylogenetic analysis of these cas genes suggests that the CRISPR loci have been propagated via HGT, horizontal gene transfer. We suggest a mechanism by which this HGT has occurred, namely, that the CRISPR loci can be carried between cells on megaplasmids ≥40 kb in length.
KeywordsRepetitive DNA Mobile genetic elements Lateral gene transfer
We would like to acknowledge Jeff Elhai at Virginia Commonwealth University for his many helpful comments regarding this manuscript. We also thank Tom Murphy, who initiated this work at the Bioinformatics and Bioengineering Summer Institute at VCU. We also acknowledge John Iverson, Kabi Neupane, and Sara Penhale for their assistance with the phylogenetic analysis.