Abstract
BACKGROUND: The dual specificity phosphatase Cdc14 has been shown to be a critical regulator of late mitotic events in several eukaryotes, including S. cerevisiae, S. pombe. C. elegans and H. sapiens. However, Cdc14 homologs have clearly evolved to regulate distinct cellular processes and to respond to regulatory signals important for these processes. The human paralogs hCdc14A and B are the only vertebrate Cdc14 homologues studied to date, but their functions are not well understood. Therefore, it is of great interest to examine the function Cdc14 homologs in other vertebrate species. RESULTS: We identified two open reading frames from Xenopus laevis closely related to human Cdc14A, called XCdc14alpha and XCdc14beta, although no obvious paralog of the hCdc14B was found. To begin a functional characterization of Xcdc14alpha and XCdc14beta, we raised polyclonal antibodies against a conserved region. These antibodies stained both the nucleolus and centrosome in interphase Xenopus tissue culture cells, and the mitotic centrosomes. GFP-tagged version of XCdc14alpha localized to the nucleulus and GFP-XCdc14beta localized to the centrosome, although not exclusively. XCdc14alpha was also both meiotically and mitotically phosphorylated. Injection of antibodies raised against a conserved region of XCdc14/beta into Xenopus embryos at the two-cell stage blocked division of the injected blastomeres, suggesting that activities of XCdc14alpha/beta are required for normal cell division. CONCLUSION: These results provide evidence that XCdc14alpha/beta are required for normal cellular division and are regulated by at least two mechanisms, subcellular localization and possibly phosphorylation. Due to the high sequence conservation between Xcdc14alpha and hCdc14A, it seems likely that both mechanisms will contribute to regulation of Cdc14 homologs in vertebrates.
