A bacterial toxin that controls cell cycle progression as a deoxyribonuclease I-like protein

Many bacterial pathogens encode a multisubunit toxin, termed cytolethal dis tending toxin (CDT), that induces cell cycle arrest, cytoplasm distention, and, eventually, chromatin fragmentation and cell death. In one such pathog en, Campylobacter jejuni, one of the subunits of this toxin, CdtB, was show n to exhibit features of type I deoxyribonucleases. Transient expression of this subunit in cultured cells caused marked chromatin disruption. Microin jection of Low amounts of CdtB induced cytoplasmic distention and cell cycl e arrest. CdtB mutants with substitutions in residues equivalent to those r equired for catalysis or magnesium binding in type I deoxyribonucleases did not cause chromatin disruption. CDT holotoxin containing these mutant form s of CdtB did not induce morphological changes or cell cycle arrest.