Editors' ChoiceMicrobiology

GTPase Implicated in Bacterial DNA Damage Checkpoint

Science's STKE  01 Mar 2005:
Vol. 2005, Issue 273, pp. tw78
DOI: 10.1126/stke.2732005tw78

In eukaryotic cells, defects in replication initiate a checkpoint signaling pathway that halts cell division so that cells are protected from deadly effects of DNA damage. Although it makes sense that prokaryotes would also benefit from such a protective response, an equivalent signaling mechanism has not been defined. A possible component of such a pathway is described by Foti et al., who used a genetic screen in Escherichia coli to identify mutations that increased sensitivity of the bacterial cells to the replication inhibitor hydroxyurea. They identified a mutation in the gene encoding ObgE, a GTPase (guanosine triphosphatase) related to Ras. ObgE is a member of a family of GTPases that are present in eubacteria and eukaryotes that have been ascribed a broad range of possible functions in various organisms, including sporulation, vegetative growth, and stress responses. In E. coli, obgE is an essential gene, but it appears also to have a function that may serve as part of a DNA damage checkpoint. Genetic interactions of obgE mutants with other mutants in genes whose products function in DNA repair supported such a role. A mutation designed to inhibit GTPase activity of ObgE did inhibit its function, but whether GTP- and GDP-bound forms of the protein serve distinct roles and whether its activity is regulated by other factors (as the eukaryotic GTPases are) remain to be explored.

J. J. Foti, J. Schienda, V. A. Sutera, S. T. Lovett, A bacterial G protein-mediated response to replication arrest. Mol. Cell 17, 549-560 (2005). [PubMed]