14-3-3 proteins are evolutionarily conserved regulatory proteins that bind to signalling proteins and affect their stability, activity or cellular localisation. Consequently, they are involved in the regulation of diverse cellular processes, including apoptosis, the cell cycle and the stress response. Here, Simo Schwartz, Jr, Julián Cerón and co-workers (p. ) investigate the function of the 14-3-3 protein PAR-5 – which is best known for its role in cell polarity – in the C. elegans adult germline, and its impact on the DNA damage response. Worms with decreased par-5 expression levels contain fewer germ cells and have smaller gonads. In addition, these germline cells contain small, fragmented nuclei, which points to a role for PAR-5 in maintaining genome stability and cell cycle progression. Indeed, the authors report that PAR-5 is involved in DNA maintenance, as depletion of the protein results in the accumulation of DNA damage. Furthermore, they find that PAR-5 is required for cell cycle arrest in response to the S and G2–M checkpoints following replicative stress and ionising radiation, respectively, and that it promotes phosphorylation of the cyclin-dependent kinase Cdk1. Thus, PAR-5 not only has a role in germline proliferation, but also acts in the checkpoint pathway to prevent premature mitotic entry in response to DNA damage.
