Cell Biology

The Kis of Life

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Science  07 Feb 2003:
Vol. 299, Issue 5608, pp. 783
DOI: 10.1126/science.299.5608.783d

A bacterial plasmid known as R1 expresses two factors that act as killer and rescuer for its host. Killing determinant (Kid) is a toxin that inhibits cell proliferation, and killing suppresssor (Kis) acts as an antidote by forming a 1:1 complex with Kid. de la Cueva-Méndez et al. show that this pair of proteins, which have evolved to kill bacteria that have lost their resident plasmid and thus the capacity to maintain synthesis of the unstable Kis component, can function in eukaryotic cells. Kid inhibits proliferation of yeast cells, Xenopus eggs, and human cells, and in each case Kis protects. In addition, Kid causes apoptosis (programmed cell death) in human cells, and this activity can be blocked by Kis, too. Thus, by regulating the relative levels of Kid and Kis, it should be possible to produce controllable, selective killing in eukaryotic cells, which may facilitate targeted lineage ablation during development or the elimination of transformed cells. — SMH

EMBO J. 22, 246 (2003).

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