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Background. Bacterial genotoxins provoke DNA damage and carcinogenesis. The Escherichia coli uropathogenic-specific protein gene, usp, and its linked genes, imu1-3, are associated with strains from pyelonephritis, prostatitis, and bacteremia of urinary tract origin. While the Usp C-terminal domain exhibits similarity with DNase-like colicins and pyocins, its role and mechanisms of action, as well as those of the 3 associated proteins, is unknown.Methods. We isolated Usp and Imu1-3 and examined their activity on plasmid DNA, human umbilical vein endothelial cells, and human embryonic kidney cells (cell line HEK293). The affect of Usp and Imu1-3 was assessed by MTT and Comet assays, infection assays, caspase 3/7 activity, fluorescently labeled actin staining, and Western blotting.Results. Usp possesses DNase activity and, particularly when coapplied with Imu2, exhibits genotoxic activity in mammalian cells. Infection assays demonstrated that E. coli usp+ imu1-3+ affects the viability of mammalian cells, induces increased caspase 3/7 activity, and perturbs cell cytoskeleton structure.Conclusions. Usp is a novel E. coli genotoxin active against mammalian cells. Optimal in vivo activity of Usp requires Imu2. Infection with E. coli usp+ imu1-3+ induces a response characteristic of apoptosis. [ABSTRACT FROM AUTHOR]

In Saccharomyces cerevisiae cells, both of the two PP2C protein phosphatases ScPtc2p and ScPtc3p and the PP4 protein phosphatase ScPph3 are responsible for ScRad53p dephosphorylation after the DNA methylation agent methylme-thane sulfonate (MMS)-induced DNA damage. In this study, we show that CaPtc2p is not required for the CaRad53p dephosphorylation during the recov-ery from DNA damage, as is CaPph3p in Candida albicans. However, deletion of CaPPH3 has an additive effect on the sensitivity of C. albicans cells lacking CaPTC2 to MMS and the DNA synthesis inhibitor hydroxyurea (HU). In addi-tion, deletion of CaPPH3 promotes in vitro filamentation of C. albicans cells. Furthermore, mutation of CaPTC2 is epistatic to that of CaPPH3 in the sensi-tivity of C. albicans cells to rapamycin. Therefore, CaPtc2p and CaPph3p might play a role in the target of rapamycin (TOR) signaling in C. albicans cells [ABSTRACT FROM AUTHOR]

In Saccharomyces cerevisiae cells, both of the two PP2C protein phosphatases Sc Ptc2p and Sc Ptc3p and the PP4 protein phosphatase Sc Pph3 are responsible for Sc Rad53p dephosphorylation after the DNA methylation agent methylmethane sulfonate ( MMS)-induced DNA damage. In this study, we show that Ca Ptc2p is not required for the Ca Rad53p dephosphorylation during the recovery from DNA damage, as is Ca Pph3p in Candida albicans. However, deletion of CaPPH3 has an additive effect on the sensitivity of C. albicans cells lacking CaPTC2 to MMS and the DNA synthesis inhibitor hydroxyurea ( HU). In addition, deletion of Ca PPH3 promotes in vitro filamentation of C. albicans cells. Furthermore, mutation of CaPTC2 is epistatic to that of CaPPH3 in the sensitivity of C. albicans cells to rapamycin. Therefore, Ca Ptc2p and Ca Pph3p might play a role in the target of rapamycin ( TOR) signaling in C. albicans cells. [ABSTRACT FROM AUTHOR]